GlossaryFind here the lexicon of eczema. Click on a letter and discover the definition of each term.


  • Aciclovir

    An anti-viral drug used to treat herpes and shingles. Aciclovir (or acyclovir) is specifically indicated for atypical or serious herpes which may appear during the course of atopic dermatitis (or even eczema herpeticum). Valaciclovir is a related drug that is transformed into aciclovir in the body. It has the same indications. Anti-virals are usually effective when taken orally.

  • Acupuncture

    Acupuncture is a technique from traditional Chinese medicine that involves placing needles in specific points around the body. Acupuncture is part of what is known as alternative medicine, alongside homeopathy, which is used by many who believe in its power to treat various conditions.  Aside from a placebo effect, which can be significant especially on the nervous state, acupuncture has no proven effects on atopic dermatitis.   

  • Aeroallergen

    An allergen in the air, such as household dust, grass pollens, and animal dander.  Inhaling aeroallergens can cause respiratory allergies (rhinitis, sinusitis, bronchitis, etc.).  It is possible that skin damage caused by atopic dermatitis allows aeroallergens to penetrate the skin. This is one of the reasons why we recommend effective treatment for atopic skin conditions in children, as in this way we may also be able to prevent aeroallergens from entering their bodies.

  • Allergen

    A molecule with the potential to trigger an allergic reaction or immunological hypersensitivity.  There are several varieties of allergen:  Certain drugs can trigger drug allergies (such as penicillin). Small molecules of nickel or chrome can cause contact eczema. Food (food allergies) Proteins present in our environment that are normal and tolerated by most people. This is the case with dust-mites for example, a significant allergen in atopy.

  • Allergy

    An allergy is an abnormal, excessive reaction of the body's immune system consecutive to contact with a foreign substance (the allergen). Allergies can take a number of forms, including eczema, asthma, hay fever, food allergies, and severe reactions to insect bites.

  • Anallergic

    That does not cause an allergy

  • Anaphylaxis

    This strange word means "the opposite of prophylaxis" or the opposite of protection. Anaphylaxis describes a substantial and acute allergy, with painful urticaria, swelling, and hypo-tension. Anaphylactic shock can be fatal if not treated quickly. It is often caused by a drug (such as a penicillin allergy).

  • Antibiotics

    Drugs that act on infections caused by bacteria. Atopic dermatitis is prone to secondary infection, which requires antibiotic treatment.

  • Antigen

    A molecule that triggers the production of antibodies to fight it. 

  • Antihistamine

    A drug that inhibits the effects of histamine. Histamine is primarily responsible for rhinitis and urticaria. It is not directly involved in atopic dermatitis, and thus anti-histamines have a limited role in its treatment.  Some anti-histamines can cause drowsiness. For this reason those taking them should be careful, for example if driving. However this calming effect is appreciated by some patients who may have difficulty sleeping, helping them deal with their pruritus. General treatments

  • Antiseptic

    A substance acting locally, on the skin for example, against bacteria and sometimes also viruses. In contrast to antibiotics, antiseptics have a broad spectrum and therefore organisms do not build resistance to them. There are several different antiseptics, each with advantages (efficacy) and disadvantages (tolerance). Chlorhexidine is currently the most commonly used. Each antiseptic has its most common usage, which should be respected in order to benefit from its advantages and not suffer from its disadvantages.

  • Asthma

    Asthma is a condition of the bronchial tubes, typified by a tendency towards broncho-constriction, that is, a narrowing of the tubes that prevents normal breathing (dyspnea, whistling, etc.). Certain types of asthma are caused by allergies. Asthma is also one example of an atopic condition, and some children with eczema are later also affected by asthma. This is what we call the "atopic career". It is difficult to prevent this development, but it is nonetheless best to remove all factors for bronchial irritation, above all smoke. Contrary to popular belief, treating eczema does not encourage asthma. In fact, by treating eczema, the risk of the skin's penetration by allergens is reduced, and thus the risk of triggering respiratory allergies such as asthma.

  • Ataxia-telangiectasia

    A rare hereditary disease, of which the symptoms are balance troubles (the meaning of the word ataxia) due to lesions on the cerebellum, as well as dilation of small blood vessels in the skin (small varicose veins, known as telangiectasia)  Children affected with ataxia-telangiectasia may also have atopic eczema and other skin conditions, including a tendency towards infection.

  • Atopy

    The term 'atopy' was coined in 1930 to describe a particular kind of immunological hypersensitivity: atopy is a hereditary tendency towards allergies to things that are found in our normal environment, such as household dust and food.   The term atopy comes from the Greek: a-topos, meaning with no precise location, that is, a condition that is not fully understood.   What is atopy? Understand easily

  • Auto-antigen

    Normally, the immune system only creates antibodies to fight antigens coming from outside the body. But sometimes the body's proteins act like antigens and can trigger an immune response. These are known as auto-antigens, and auto-immune diseases. In atopic dermatitis, epidermal proteins that have been damaged by inflammation and scratching can become auto-antigens, which prolongs inflammation. 

  • Anaphylactic shock

    A state of shock is an acute circulatory failure (syncope, hypo-tension). Anaphylactic (see term) shocks are acute allergies which require emergency treatment. 

  • Atopic dermatitis

    A term commonly used in all languages to describe inflammatory dermatitis related to atopy. The term "atopic eczema" is a synonym. In certain countries, the older term "Neurodermatitis" is sometimes used. What is atopic eczema?

  • Atopic diathesis

    "Diathesis" is a word taken from old French, which has practically disappeared from medical terminology. Atopic diathesis is therefore rarely spoken about, but it is basically a synonym for a tendency towards atopy: hereditary predisposition to atopic conditions: atopic dermatitis, allergic rhino-conjunctivitis, asthma, etc. 

  • Atopy school

    (See also Atopy workshop). Generic term describing organizations that offer atopic patients (adults, children and their parents) educational workshops and sessions about the various aspects of the condition and the best way to improve it. As with other chronic diseases, atopic dermatitis benefits from therapeutic education, as it improves information, reduces worry, and facilitates correct and effective use of treatment. Our Atopic Dermatitis Foundation's website provides a lot of useful information about joining atopy schools or workshops: Find an expert 

  • Atopic eczema

    A synonym of atopic dermatitis.  If you are looking for information about the condition, for example using a search engine on the internet or medical journals, it is better to use the term atopic dermatitis as it is the most commonly used term.  In everyday life we talk about eczema. What is atopic eczema?

  • Adaptive immunity

    Part of the immune system that reacts by adapting specifically to antigens, thanks to receptors carried by lymphocytes or blood cells (antibodies). The main cells in adaptive immunity are T lymphocytes (carriers of receptors for antigens) and B lymphocytes, which make antibodies. All the various parts of the immune system work together, and cells in the adaptive immune system are activated by mechanisms in the innate immune system.  

  • Auto-immune disease

    Normally, the immune system reacts against foreign bodies (most commonly microbes). In auto-immune diseases, it reacts against normal cells or organs of the body, which causes problems at organ level. For example, some kinds of thyroid disease are caused by auto-antibodies, which attack the normal components of the thyroid. Some bullous conditions (pemphigus, pemphigoides) are caused by anti-skin antibodies.   

  • Atopic career

    The term atopic career is often used to describe the fact that, often, different atopic conditions appear gradually over time: atopic dermatitis in infants, asthma in older children, and later rhino-conjunctivitis. However, this is not necessarily always the case, and the majority of children who suffer from atopic dermatitis do not go on to develop asthma. This idea is nonetheless worth investigating. For example, the current thinking is that epidermal abnormalities (such as filaggrin deficiency) encourage the penetration of allergens, which may later provoke respiratory allergies. Thus, by effectively repairing the epidermis using emollient and anti-inflammatory treatments, we may hope to prevent this sensitization. These latest scientific ideas are in fact the opposite to the old wives tale, which says that it is a bad idea to "force out" eczema - a dangerous and harmful idea.

  • Anti-microbial peptides

    Substances naturally produced by the epidermis, with anti-bacterial properties. Antimicrobial peptides, or natural anti-biotics, are part of the innate immune system, and play an important role in defending the skin against infection, as well as playing other roles in the epidermis.

  • Allergy tests

    A general term for a range of tests designed to prove an immunological sensitivity or allergy. As a general rule, allergy tests should be treated with caution, and assessed alongside the patient's complaints.  There are two types of allergy test:  In vitro or laboratory tests, carried out on a blood sample. These are used to measure total IgE (allergic antibodies) as well as specific IgEs for a certain allergen. There are also more specialized tests which are reserved for research protocols.   In vivo tests, carried out on the living patient. A potentially allergizing substance is administered to the patient to test whether it provokes a reaction. Of course, any such tests should be carried out by an experienced doctor, who knows how to implement them in such a way as to be certain that the results are accurate and useful, and also how to interpret them. Some of these tests may be helpful with regard to atopic dermatitis: intradermal or prick tests with immediate reading of results to prove atopic sensitivity, contact or patch tests with delayed reading to diagnose contact eczema, with an added atopy patch test in certain circumstances.


  • Essential fatty acids

    Fatty acids are simple lipids that play a part in several metabolisms and are also part of the structure of cell membranes. Some of them are deemed essential because the body is not able to synthesize them; they must therefore be obtained through diet. The epidermis manufactures complex lipids (ceramides) that contain essential fatty acids. Abnormalities in these lipids have been observed in cases of atopic dermatitis, and it is thought that this could be corrected by providing these essential fatty acids either by topical or oral treatment. However, attempts to improve AD using oils containing essential fatty acids (evening primrose oil, borage oil, etc.), particularly those containing omega-6 such as linoleic acid, gave disappointing results.

  • Egg allergy

    Allergy to egg is one of the major food allergies. Certain children with atopy are allergic to eggs. But as always with allergies, one should be careful not to confuse positive tests with real allergy, and remember that aside from cases with digestive complaints, it is pointless to test atopy sufferers for food allergies.

  • Epidermal barrier

    (or skin barrier) The skin is the interface between the organism and the outside world. The skin represents a barrier against dehydration and the penetration of undesirable elements, such as germs, allergens or toxic chemical products. When the skin is dry (xerosis) or inflamed (eczema), the role it plays as a barrier is defective.

  • EASI

    Eczema Area and Severity Index This is a scale that helps to rate the surface and severity of atopic dermatitis. The EASI score is often used by American dermatologists for clinical trials. In Europe, the more commonly used scale is the SCORAD. Learn more 

  • Eczema of the eyelids

    The skin of the eyelids is particularly thin and is thus subject to eczema reactions. Atopic dermatitis in older children and adults often affects the eyelids. A classic cause of eczema of the eyelids is allergy to nail varnish. The nails themselves are not affected due to their thickness, however the thinnest areas of skin that are touched by the fingers (neck, eyes, etc.) can present with eczema lesions.  Learn more

  • Eczema herpeticum

    This Latin term is used in medical texts to describe severe herpes which can complicate atopic dermatitis. In French, it is often known as "Kaposi-Juliusberg varioloform pustules". Basically, atopic skin is particularly vulnerable to infection by the herpes virus. This is not too serious, but most often requires oral antiviral treatment.

  • Eczematides

    A vague dermatological term describing non-acute eczema. Atopy sufferers may present with eczematide-like eruptions.

  • Emollient

    An emollient is a cream or ointment that moisturizes and softens the skin. Hydrate your skin to prevent flare-ups

  • Eosinophils

    One of the categories of polynuclear blood cells (or white blood cells). The number of eosinophils in the blood is increased in parasitic conditions, allergic conditions, and certain rare diseases. In atopic dermatitis, there is often a moderate increase in blood eosinophils, with no practical impact.

  • Epidermis

    The outside layer of the skin. The epidermis is typified by a gradual differentiation of cells which become flattened and dehydrated. These cells, called corneocytes, make up the stratum corneum, which creates the solid structure of the epidermis and plays the role of barrier or interface with the outside world. In atopic dermatitis, there are a number of epidermal abnormalities which are thought to be the cause of the condition.

  • Erythema

    Skin redness.

  • Erythroderma

    A serious skin condition, where the skin is entirely red and inflamed. There are many causes of erythroderma: atopic dermatitis, psoriasis, lymphoma, drug reactions and genetic conditions. Erythroderma is prone to complications (infection, dehydration, etc.) and generally requires treatment in hospital.


    An acronym: European Task Force on Atopic Dermatitis. A group of specialists who developed the SCORAD (see also: Task Force).

  • Exclusion diet

    A diet that is altered so that it does not contain (excludes) a type of food that the subject reacts badly to. For example, those allergic to gluten follow a gluten-free diet. Exclusion diets should be followed on the advice of, and under supervision by a doctor. The diet should maintain the necessary nutritional qualities the body needs. Exclusion diets can otherwise cause excessive and unnecessary nutritional deficiencies.

  • Excoriation

    A superficial skin wound, generally due to violent scratching. It can be liable to infection. Excoriation is one of the complications of the itching that is part of atopic dermatitis.

  • Extrinsic

    From the outside. Some researchers have attempted to distinguish between extrinsic atopic dermatitis (caused by allergies) and intrinsic atopic dermatitis (with no allergic cause). This distinction has no practical impact.

  • Epidermal hyperplasia

    A histological term describing increased thickness of the skin. This is often seen in atopic dermatitis.

  • Epidermal lipids

    Epidermal lipids are an important part of the stratum corneum. They can be compared to cement that surrounds the "bricks" of the cells, or corneocytes. Epidermal lipids are made of sterols, fatty acids and ceramides. They maintain the integrity of the stratum corneum, and thus the barrier function. When these lipids are altered, the role of the epidermis is compromised, and only emollient treatments can repair this. In atopic dermatitis modification to epidermal lipids plays a major role, alongside protein anomalies such as filaggrin deficiency, however, little is known about it.

  • Edema

    Swelling caused by the presence of liquid in tissues. Swollen legs in patients presenting with venous insufficiency is an example of edema. There is no significant edema in atopic dermatitis, because the liquid caused by inflammation is able to escape the skin as weeping.

  • Elimination diet

    Removal of a specific foodstuff from a child's diet. A real allergy to one type of food justifies the removal of this food from the child's diet. However, food should not be eliminated without a medical reason. Elimination diets are not necessary for atopic dermatitis, unless the patient also suffers from digestive difficulties, and has had an accurate allergological and nutritional examination. Remember that food allergies are very rare in children who are affected with atopic dermatitis with no digestive symptoms.

  • European task force

    An international group of atopic dermatitis specialists, who have met regularly for around 20 years. Most notably, they developed the SCORAD. In English, the group is known as the ETFAD: The European Task Force on Atopic Dermatitis.

  • Exclusion diet test

    A test consisting in removing one type of food from the diet, to see whether this will improve a condition. In general, this is followed by a reintroduction (or provocation) test, to find out whether re-including this food type triggers symptoms again. These tests are rarely used in atopic dermatitis cases, and are hard to interpret.

  • Epicutaneous tests

    See Patch tests.


  • Breastfeeding

    Breastfeeding has many advantages over bottle feeding. These advantages are both psychological and nutritional. Furthermore, it is thought that delaying the introduction of non-human proteins (cow's milk) into the diet of infants can prevent atopic dermatitis and other manifestations of atopy. However, following several clinical trials, we now know that even prolonged breastfeeding does not prevent atopy. In conclusion, we should encourage mothers to breastfeed, but should not promise that this will prevent allergies, and should also avoid shaming those who choose to bottle feed.   

  • Bacteria

    Micro-organisms which may be well-tolerated by the body, but can also be responsible for infection. The primary bacteria that can cause infection in cases of atopic dermatitis are staphylococcus aureus.

  • Basophil

    One of the categories of white blood cells, thus called because of their reaction to the colorants used to count blood cells. There are very few basophils, or polynuclear basophils, compared to other cells, but they are involved in some allergic reactions.

  • Betamethasone

    One of the most commonly used corticosteroids. Betamethasone valerate and betamethasone dipropionate are the active ingredients in very effective dermo-corticosteroids.

  • B Lymphocyte

    A variety of lymphocyte, with the fundamental role of manufacturing antibodies (including, among others, IgE). The letter B refers to the fact that in birds, these cells are differentiated in an organ found in the cloaca, and known as the Bursa of Fabricius. There is no equivalent in humans.

  • Bounce back

    A flare-up of a condition followed by an improvement. For example, in atopic dermatitis, local corticosteroid therapy rapidly improves an eczema flare-up. Once improvement is seen it is recommended to gradually decrease treatment in order to prevent relapse.


  • Food allergy

    The relationship between food allergies and atopic dermatitis are very complicated, and can often confuse parents. In practice, we must remember that they are two independent conditions: atopic dermatitis is not caused by a food allergy, and it is useless to carry out tests. It is also useless to attempt elimination diets or other investigations unless the patient also suffers from digestive symptoms.

  • Filaggrin

    A very important molecule found in the epidermis. Its name comes from its primary function, which is to gather, or keep together, keratin fibers, which are important for the form and function of epidermal cells. During epidermal differentiation, filaggrin, which is present in its complete form in the granular layer, is degraded by enzymes called proteases, forming smaller molecules that play an essential role in epidermal hydration (Natural Moisturizing Factor). The current interest in filaggrin comes primarily from the fact that in 2006, British researchers discovered genetic anomalies in filaggrin in patients suffering from atopy, and they are therefore a risk factor for atopic dermatitis and other atopic conditions.

  • Follicular

    An adjective referring to anything related to the skin's hair follicles. Dermatitis found primarily around the hair follicles is known as follicular eczema or follicular dermatitis. For example, rough skin on the arms is known as keratosis pilaris, or follicular keratosis.

  • Fish oil

    An animal oil that is particularly rich in vitamin D and in omega-3 essential fatty acids. The most commonly known type is cod liver oil. Vitamin D is currently administered as a medical prescription. An omega-3 supplement has no particular role in treating atopic dermatitis.

  • Fingertip unit

    One of the major difficulties in dermatology is quantifying local treatments. Whilst it is easy to swallow, for example, one tablet per day, it is difficult to apply a precise amount of local (topical) treatment to the skin. The quantities applied depend on the product's consistency and the way in which it is applied. Its absorption depends on the area of the body being treated, the skin's condition (normal or abnormal) and many other factors (age, clothing, etc.). Some dermatologists recommend stating the quantity that should be applied by counting 'fingertip units'. One fingertip unit is the amount of cream or ointment that fills a fingertip (down to the first joint) of the index finger as it comes out of the tube. This unit is not very precise, but corresponds to about 500mg, which is the quantity needed to treat around 250cm2 of skin (a rectangle of 25cm by 10cm). This is complicated and not commonly used in practice. However, it is true that the amount of treatment used needs to be counted in some way, particularly when using dermo-corticosteroids. In this case, attention should be paid to ensure the amount applied does not exceed the dose recommended by the doctor, and to use small quantities, reducing them once improvement is observed.

  • Flare-up

    Atopic dermatitis is a chronic condition that develops in flare-ups in between periods of remission. Flare-ups are often triggered by stress, whether psychological or otherwise. During a flare-up, the patient may experience significant inflammation that may require local corticosteroid therapy. During remission periods, emollient treatments and preventive measures are normally enough.


  • Contact allergy

    Eczema caused by allergizing substances applied to the skin. The most common form of contact eczema is caused by metal objects containing nickel (costume jewelry, other accessories)   Learn more 

  • Cyclic AMP

    A small molecule that plays a very important role in several of the body's functions. Several studies have shown that atopic conditions involve an abnormal increase in an enzyme known as phosphodiesterase, whose role is to degrade cyclic AMP. Thus, cyclic AMP is reduced in white blood cells (leukocytes), causing abnormal reactivity. Phosphodiesterase inhibitors could therefore help to correct cell anomalies in atopy. They are currently undergoing clinical trials for asthma and atopic dermatitis.

  • Candida albicans

    A microscopic fungus that is present in tiny quantities in the digestive system. Sometimes Candida albicans can colonize the skin, which creates pustules.

  • Cataracts

    When the lens of the eye becomes opaque, causing loss of vision. Cataracts are common in older patients. Very rarely in atopic conditions, bilateral cataracts can appear during adolescence. Treatment with oral corticosteroids may cause cataracts, but it has been proven that those used to treat atopic dermatitis do not increase the risk of cataracts.

  • Ceramides

    A class of lipids with a high molecular mass, found in cell membranes, as well as surrounding epidermal cells in the stratum corneum. Some studies have shown anomalies in epidermal ceramides in cases of atopic dermatitis. These anomalies contribute to the deficiency of the epidermal barrier function

  • Cheilitis

    Inflammation of the corner of the mouth. This is sometimes simply eczema, or even irritation. Sometimes it can be a bacterial or fungal infection. 

  • Chemokines

    A certain kind of cytokine, whose fundamental role is to attract cells, particularly at the site of inflammatory reactions. The most commonly known chemokine is called interleukine 8. 

  • Chlorhexidine

    A commonly used antiseptic, found in many treatments.  Chlorhexidine is effective and well-tolerated. One should be aware of the recommended use before using a product containing chlorhexidine.  

  • Claudins

    Molecules with a role in certain bonds between epidermal cells known as tight junctions. Their role is fundamental to the efficacy of the barrier function.

  • Climate therapy

    Climate therapy uses the beneficial effects of climate for health. This usually means sunnier climates (also known as heliotherapy). Hydrotherapy courses often combine hydrotherapy treatment using water with medical properties alongside climate therapy treatment.

  • Comorbidity

    Comorbidity is used to describe a patient affected with several diseases. For example, psoriasis and arterial hypertension. In the case of atopic dermatitis, the coexistence of asthma is generally described as an atopic condition or a dermo-respiratory syndrome.

  • Conjunctivis

    An inflammation of the conjunctiva (white of the eye). It can be caused by allergies.

  • Contagion

    Contagion means the direct or indirect transmission of a disease. Eczema is not contagious.

  • Corneocyte

    The major cells of the epidermis are known as keratinocytes. In the stratum corneum, the uppermost layer of the epidermis, they are flattened and lose their nucleus. These are known as corneocytes.

  • Corticophobia

    Corticophobia, or a phobia about corticosteroids, is an excessive fear of these drugs that are very useful in treating atopic eczema. Do cortisone creams have side effects?

  • Cosmetics

    Cosmetics are products that are applied to the skin with a superficial effect. There are two types: Appearance-altering cosmetics (make-up, lipstick, etc) are used to make the skin appear more beautiful. Cosmetics known as 'active' have the role of improving certain properties of the skin. For example, they can moisturize, improve texture, or protect against the sun. Cosmetics are subject to strict regulation that is different to that applied to drugs. Certain cosmetics may be poorly tolerated (causing irritation or allergies) but currently this is rare. Skin hydration is a daily necessity for atopic dermatitis sufferers. Moisturizing products that act on the skin's uppermost layers may have the status of 'cosmetics'. Some have obtained a 'drug treatment' status due to their properties. Others have a halfway-measure status of medical device (MD). From the user's point of view, these regulatory differences are of little importance.  

  • Cream

    An emulsion made of active principles and excipients, to create a treatment for local use or a dermo-cosmetic product. Creams are generally rich-feeling and pleasant to use. Ointments are more oily and thick, whereas gels are more fluid. Emollients’ nourishing power

  • Crust (or scab)

    When a biological liquid (such as blood, pus or serum) dries or coagulates, it forms a solid crust.  For example, weeping eczema will form yellowish crusts. Local treatment is required to quickly remove these crusts, which may otherwise be subject to secondary infection. 

  • Cradle cap

    This colloquial term describes squamae (flakes) on the scalp in seborrheic dermatitis in infants, a benign condition that actually has nothing to do with cradles! Cradle cap is very different to eczema of the scalp in atopic infants: they are not itchy and do not weep. Eczema vs seborrheic dermatitis

  • Cushing's Syndrome

    An endocrine disorder caused by excessive production of the hormone cortisol by the adrenal glands. General corticosteroid treatment in high doses can cause drug-induced Cushing's Syndrome. Dermo-corticosteroids, when used correctly, never cause such complications.

  • Ciclosporine​​​​​​​

    A powerful immunosuppressant drug, used primarily to prevent organ rejection in transplant cases. Ciclosporin is also used in certain serious cases of inflammatory conditions, such as atopic dermatitis. These cases are exceptional, and treatment should not last too long as ciclosporin can have serious side effects.

  • Cytokines

    Molecules created by certain cells, and acting at a distance on others (cyto- from the Greek for cell). Interleukines, chemokines, and growth factors, among others, are all cytokines. Cytokines are present everywhere in the immune and inflammatory systems. Anti-inflammatory treatments aim to counteract the action of inflammatory cytokines.

  • Congenital immune deficiency

    A genetic condition typified by a deficiency in the components of the immune system. This manifests itself through frequent and serious infections. Certain specific immune deficiencies are accompanied by eczema which resembles atopic dermatitis, such as Buckley syndrome, hyper-IgE syndrome or Wiskott-Aldrich syndrome, for example. In common cases of atopic dermatitis, the skin is vulnerable to certain infections (staphylococcus, herpes, etc.) but there is no immune deficiency.

  • Contact dermatitis

    Inflammation of the skin caused by contact with certain substances. There are two types of contact dermatitis: Irritation dermatitis, also known as irritant contact dermatitis. Allergic contact eczema. In practice, it is never easy to tell the difference between the two. People working in an environment where they are exposed to irritants or allergens (hairdressers, builders, certain industrial environments) should take special precautions. Learn more

  • Contact eczema

    Secondary eczema following contact with substances that trigger a specific immune reaction. The most common causes of contact eczema are nickel (costume jewelry) and chrome (cement). Local drug treatments and cosmetics can, in rare cases, cause contact eczema.  Contact eczema appears where the allergizing substance (contact allergen) was in contact with the skin. Proof can be found using epicutaneous testing or patch tests. The suspected substances are applied to the back, in controlled conditions. After 48 hours of application, it is possible to see whether the substance has caused a patch of eczema to appear.   Learn more

  • C fibers

    A type of nerve fiber found in the skin that play a role in pruritus (itching). They are stimulated by histamine.

  • Chinese herbs

    Traditional Chinese medicine uses herbal mixtures. There are thousands of them. Several years ago, it was thought by several authorities that Chinese herbs, when drunk in the form of an infusion, could have a significant effect on atopic dermatitis. However hopes were dashed, and this is unsurprising as prescriptions in Chinese medicine are personalized and respond to other criteria than those used by conventional science.   

  • Calcineurin inhibitors

    Immunosuppressant drugs, thus named because they suppress, or inhibit, certain immunological reactions. They are used systemically to prevent rejection of organs following transplant (kidney, heart, etc.). Ciclosporin and tacrolimus are examples.  When used locally, tacrolimus and its derivative, pimecrolimus (not sold in France) have an anti-inflammatory action similar to dermo-corticosteroids. They are therefore effective in treating eczema, and particularly atopic dermatitis.

  • Cow's milk proteins

    Milk is rich in lipids, glucides, and proteins, such as lactalbumin. In contrast to the proteins found in human milk, the proteins in cow’s milk (and other mammals) can be allergenic. Allergies to cow’s milk proteins cause digestive upset. There is no reason to believe that a child suffering from atopic dermatitis is allergic to cow’s milk or any other food unless they also suffer from digestive disorder. Eczema and cow’s milk

  • Chickenpox

    A childhood illness caused by the varicella-zoster virus, from the herpesviridae group. Chickenpox is practically compulsory for children. It appears as small red vesicles all over the body. It can leave scars, especially if the lesions are scratched or become infected. There is a vaccine against it, but it is only recommended for children in certain circumstances. Chickenpox has no specific effect on atopic children. 


  • Therapeutic education workshop

    A forum dedicated to the treatment of patients suffering from chronic diseases: psoriasis, asthma, diabetes  ...

  • Therapeutic education (TPE)

    A collection of measures facilitating an improvement in patients' awareness of their condition and its treatment. Compared to a traditional medical consultation, therapeutic education aims to mobilize the maximum number of people (doctors, nurses, psychologists, etc.) and leave patients plenty of time to express their concerns and receive specially-adapted information. Therapeutic education improves the patient's understanding of the condition, reduces anxiety, and facilitates correct treatment. The result is an improvement in the condition's symptoms and its psychological and social consequences.  Eczema: therapeutic education offers effective support

  • Topical immunosuppressor

    This is a new class of local drugs for eczema. (They are not dermocorticosteroids.) They are very effective, but must be used with caution and on doctors' orders.

  • Transepidermal water loss

    In its normal state, the epidermis loses small quantities of water through evaporation - this is known as insensible water loss, as the subject does not notice it is happening. This evaporation is a good marker for epidermal integrity and barrier function. If these are compromised, much more water escapes the epidermis and insensible water loss increases. One of the ways to prove a treatment has improved the condition of the epidermis is to measure transepidermal water loss, which should have diminished. 

  • T-helpers

    see TH1 et TH2.

  • T-regulators

    A subset of T cells which help to maintain immune responses at the correct level preventing them from growing out of control. A deficiency in T-regulator lymphocytes causes excessive immune responses: auto-immune diseases and possibly allergies.

  • Tachyphylaxis

      A pharmacological term that is not commonly used. It describes the concept that when a drug is too commonly or inappropriately used, it loses its efficacy. For example, local corticosteroids should not be applied more than twice a day. 

  • Tacrolimus

    Tacrolimus (commercially known as Protopic®) is a topical anti-inflammatory drug. It acts in a different way to corticosteroids. It is a calcineurin inhibitor. The same molecule when used for systemic treatment acts as a powerful immunosuppressant (Prograf®), used to prevent organ rejection in transplants. Topical tacrolimus is an effective and well-tolerated treatment for atopic dermatitis. As with all drugs, one should always follow the indication, counter-indications and directions for use. Sometimes when beginning treatment with tacrolimus, sensations of heat or discomfort may be felt, but they are generally moderate and temporary.     Medications used to treat eczema  

  • TH1 and TH2

    T means T lymphocytes (differentiated in the thymus), which are blood cells responsible for many immune reactions. H means "helper". Thus, TH1 and TH2 are T lymphocytes that work together and with other cells to increase immune responses. They are often called CD4 or CD4+ lymphocytes, as they express the surface protein CD4. There are several subsets of T-helper lymphocytes, known by number: TH1 are primarily involved in defense against certain microbes, TH2 are involved in stimulating B cells to produce antibodies, including IgE. In atopic dermatitis and atopy in general there is an imbalance between these subsets; TH2s are more numerous or more active than in non-atopic subjects.

  • Thalassotherapy

    Treatment using seawater. This generally involves a visit to a center for baths, treatments and a special diet. Thalassotherapy is a sort of "well-being cure" for healthy people with no medical aim.

  • Thermalism

    Treatment using mineral spring waters. The word thermal indicates that the water is warm, but this is not always the case. Thermalism is a medical treatment carried out at hydrotherapy centers that have been built around water sources where the water has special properties. Each center has its own special indications: Avène, La Roche-Posay, and Uriage specifically treat skin conditions; Aix-les-Bains, Dax and others treat rheumatism, and La Bourboule and others respiratory conditions. Thermal or hydrotherapy treatments obey strict medical regulation: they are prescribed by a doctor and reimbursed by medical insurance. They last three weeks, including a program of treatments that are carried out under direction from medical specialists.  Alongside this traditional program, the patients benefit from a holistic medical, psychological, educational and environmental support for their condition.    

  • Thymus

    An organ of the immune system located at the base of the neck. 

  • TNF-alpha

    Tumor Necrosis Factor. This factor has many biological properties, but is primarily involved in chronic inflammatory conditions such as rheumatism or even psoriasis. Anti-TNF antibodies are effective treatments for these inflammatory conditions. 

  • Toll-like receptors

    Receptor resembling the roll receptor of the Drosophila fly, which help cells to recognize microbes and thus trigger defense reactions. These receptors are part of innate immunity (see this term). There are around ten types of toll-like receptor or TLR. They are important in dermatology as they are found in keratinocytes, and represent the first line of defense against infection. They also have other properties.

  • TSLP (cytokine)

    Thymic Stromal Lymphopoietin. TSLP was initially isolated from a strand of thymic cells, hence its name. However, it is also secreted by other cells, including keratinocytes. Its role is to activate lymphocyte differentiation in favor of TH2 cells. It is currently thought that TSLP plays an important role in atopic dermatitis, as it is activated by epidermal abnormalities, and stimulates TH2 cells, and thus triggers stimulation of B lymphocytes to produce antibodies including IgE. Thus, TSLP is a link between epidermal abnormality and allergic inflammation.


  • Skin biopsy

    A small sample of skin taken under local anesthetic using a special tool, like a tiny hole-punch. The fragment taken is then observed under the microscope, facilitating a diagnosis of the skin condition which may not be possible in a clinical setting. In atopic dermatitis, only certain unusual cases need skin biopsies. Skin biopsies leave minimal scarring.

  • Scratching

    The action of scratching the skin, a result of pruritus (itching). In atopic dermatitis, when pruritus is intense and chronic, scratching may cause alterations to the skin, for example a thickening (known to dermatologists as lichenification). Managing scratching using various different methods is one of the important aims of atopy workshops and schools.  

  • Specific desensitivation

    A technique for allergy treatment that consists in regular injections of small doses of allergens, with the aim of provoking an immunological reaction that will reduce or eradicate the allergy. In some cases, such as allergy to insect poison, desensitization is an effective treatment. However, in atopic dermatitis, even if positive test results are seen, desensitization does not result in an improvement.

  • Sub-auricular fissure

    A crack in the fold of skin below the ear, caused by atopic eczema. It appears often and may be painful and subject to secondary infections.

  • Soap

    Soaps are chemical products that are able to solubilize fats and dirt, helping to remove them. This effect is known as detergent or surfactant, and is useful for cleansing the skin, however it can be irritating. Syndets (synthetic detergents) are less irritating cleansing products.   Cleansing and skin care  

  • Spink 5

    (serine protease inhibitor Kazal type 5), a gene that encodes the protease inhibitor known as LEKTI (lympho-epithelial Kazal-type inhibitor) which is mutated and thus inactive in Netherton syndrome.

  • Spongiosis

    A histological term describing the fact that in eczema, epidermal edema separates cells that are normally joined together. This causes an appearance similar to a sponge.

  • Staphyllococcus

    Bacteria commonly present in our environment. Certain staphylococci are generally harmless (staphylococcus epidermidis), whereas others, such as staphylococcus aureus, can create potentially serious infections. Skin affected with atopic dermatitis is particularly susceptible to staphylococcus aureus. However, its presence generally causes no harm. This is known as colonization. However, they can cause infections. In such cases antibiotic treatment is necessary. What complications are associated with atopic eczema?

  • Stratum corneum

    A Latin term used in French and English medical literature, meaning the cornified or horny layer. It is the outermost epidermal layer, and is in contact with the outside world. The stratum corneum plays the most important role of the epidermis; the barrier function. Abnormalities in the stratum corneum have been observed in atopic dermatitis, the most well-known being filaggrin deficiency.

  • Stratum granulosum

    A Latin term used in French and English medical literature, meaning the "granular layer". This is the layer that lies directly below the stratum corneum. It takes its name from the number of granules that can be clearly seen under the microscope. These granules, which are made of keratohyalines, contain primarily profilaggrin, a precursor of filaggrin.

  • Streptococcus

    A microbe that is part of the group of Gram positive cocci. Streptococci are often responsible for infections: tonsillitis, respiratory infections, and skin infections such as some types of impetigo and erysipelas. Eczema lesions can be subject to secondary infection by streptococcus. Before the discovery of antibiotics, streptococci could cause serious complications, particularly for the heart and kidneys.

  • Stress

    Stress is used to describe all types of aggressions, and the body's response to these aggressions. Emotional stress, whether linked to anxiety, difficult situations, personal problems, family or professional issues, are the primary cause of flare-ups in atopic dermatitis. Eczema and emotions

  • Sweat

    Sweat or perspiration is the body's normal response to excess heat. Perspiration can also be caused by emotion. Sweating (due to heat or effort) can also cause itching in atopic dermatitis. Advice and tips so that you have total freedom to play sports!

  • Superantigen

    An immunological term used to describe microbes whose property is to trigger large scale reactions.

  • Syndets

    A term originally from America, meaning (synthetic detergents). They are chemical products with a surfactant effect, similar to soaps but less aggressive, and closer in pH (acidity) to the skin's natural level. Dermatological bars are syndets.

  • Smallpox vaccination

    Discovered by Jenner in 1776, the smallpox vaccine was a considerable medical breakthrough. It helped eradicate smallpox, and the last case was seen in 1977. Since then, smallpox vaccination has not been compulsory, but it may be reintroduced, for example for military personnel in the case of bioterrorism. Atopic dermatitis is affected in this case as it is contra-indicated for smallpox vaccination, which can cause serious infections known as eczema vaccinatum, similar to eczema herpeticum.


  • Dendritic cells

    Cells that are part of the immune system, with the primary function of presenting antigens to lymphocytes. Langerhans cells are epidermal dendritic cells. Dermal dendritic cells also exist. 

  • Diagnostic criteria

    These are symptoms which allow doctors to be certain that the diagnosis of atopic dermatitis is correct. For example, the appearance of eczema, itching, chronic development pattern, etc. In fact, these criteria are primarily used in large-scale clinical studies. In practice, diagnosis of atopic dermatitis (or eczema) is generally not difficult.

  • Defensis

    Molecules with antimicrobial properties produced by the skin. They are often described as natural antibiotics.

  • Depigmentation

    Discoloration or lightening, even whitening of the skin. This is the only symptom of certain conditions such as vitiligo. Significant inflammation as seen in atopic dermatitis can cause skin pigmentation problems (or dyschromia)

  • Dermatophagoides

    The scientific name for the dust-mites that live in household dust. Allergy to these mites (Dermatophagoides pteronyssinus) plays a role in asthma and certain kind of rhinitis. Although atopic dermatitis patients may be recommended to keep their living environments clean, the significance of dust-mite allergy is still in debate, and is likely only a minor factor.

  • Dermatophytes

    Microscopic fungi with a particular affinity for the stratum corneum. They are therefore responsible for infections of the upper skin layers: ringworm of the scalp in children, rounded plaques on the skin, intertrigo (particularly athlete's foot) and fungal nail infections, particularly on the toes.

  • Dermatosis

    From the Greek "derma" = skin. Dermatoses means all skin conditions, independently from their cause.

  • Dermocorticosteroids

    Medications used in dermatology due to their anti-inflammatory effect on dermatoses (skin disease). For example, eczema, psoriasis. Learn more 

  • Dermographism

    Dermographism is sometimes known as 'skin writing': simply scratching or rubbing the skin provokes a line of urticaria which is red and raised. It can be a benign reaction, and if so will not be accompanied by itching. Recent and itchy dermographism is the same as urticaria, and should be investigated as such (treatments, diet, etc.).

  • Desquamation

    The medical term to describe the formation of squamae or scales/flakes on the skin's surface. This is also described as peeling skin. Certain conditions are typified by significant desquamation. The most commonly known of these is psoriasis. Chronic eczema involves thickened skin that sheds squamae.  

  • Dyschromia

    Pigmentation (or color) anomaly in the skin. We distinguish between hyperpigmentation, where the skin is darker than usual (e.g. melasma), and hypopigmentation, where the skin is lighter than usual (e.g. vitiligo). Skin inflammation, such as is seen in atopic dermatitis, can cause temporary dyschromia.

  • Dyshidrosis

    A type of eczema that affects the palms of the hands and soles of the feet, as well as the sides of the fingers and toes. Dyshidrosis is typified by small blisters filled with serous liquid (vesicles), that are very itchy. All eczema, atopic dermatitis included, can present as dyshidrosis. Contrary to what one may gather from its name, dishydrosis has nothing to do with sweat. The thickness of the stratum corneum in these areas is probably responsible for this curious appearance.

  • Delayed hypersensitivity

    A kind of allergy in which clinical symptoms appear later (several hours to several days) after introduction of an allergen. The best example of these is allergic contact eczema. Hypersensitivity, immunity, or delayed allergy, does not involve antibodies as do other immune responses, but rather T lymphocyte cells only.

  • Dermo-epidermal junction

    Area that separates the epidermis from the dermis, often known as the basal membrane or layer. The dermo-epidermal junction is made up of several structures (collagens, adhesion molecules, etc). Conditions affecting the dermo-epidermal junction can be hereditary (bullous epidermolysis), or acquired (bullous auto-immune diseases). Atopic dermatitis does not affect the dermo-epidermal junction.

  • Dennie-Morgan fold

    A double skin fold (wrinkle) under the lower eyelid, which is often seen in people affected with atopic dermatitis. It is one of the minor criteria for diagnosis, and thus has little value.


  • Preservatives

    Most cosmetics and topical treatments need protection against microbial contamination, during manufacture as well as during use. This protection is provided by anti-microbial substances known as preservatives. The use of preservatives is strictly regulated (national and European regulation) and all preservatives currently used have an excellent level of efficacy and safety, even if there are rare cases of intolerance by certain individuals. The major preservatives are parabens, alcohols, formalin, triclosan, kathon, Euxyl and other chemical substances. Certain manufacturing processes and use of sterile environments (sterile cosmetics) facilitate the omission of preservatives.

  • Peri-ocular dermatitis

    Inflammation around the eyes. This is often combined with peri-oral dermatitis

  • Peri-oral dermatitis

    Inflammation (redness) around the mouth. There are many potential causes of peri-oral dermatitis. Paradoxically, it can be a reaction to excessive or inadequate use of dermo-corticosteroids on the face. Peri-oral dermatitis is benign but can be long-lasting. 

  • Palmar hyperlinearity

    Excessive visibility of lines on the palm of the hand, which is one of the minor (less important) criteria for atopic dermatitis.

  • Papillomavirus

    Virus responsible for human papilloma. The main types are warts, laryngeal papillomatosis, and genital warts.

  • Papule

    A solid, raised skin lesion (not liquid filled).

  • Parabens

    This term describes preservative: parahydroxy methyl benzoate, ethyl,  propyl, butyl, de methyl. Parabens are effective against bacteria and fungi, which explains their common use. As with all components of cosmetics, parabens have been the subject of extensive toxicological studies (on their estrogenic and carcinogenic effects) and their use is now considered to be free of danger to health. However, the debate rages on.

  • Patch tests

    The name for epicutaneous tests, carried out by applying suspected substances to the back. This helps diagnose allergic contact eczema. A positive test appears as in a small eczema lesion, which will be visible for 48 to 72 hours after the test is applied. The term atopy patch test refers to epicutaneous tests carried out not with contact allergens, but with allergens suspected to play a role in atopic dermatitis, such as dust-mites. Their usefulness is subject to debate. Identifying the cause of eczema through allergy tests

  • PH

    A chemical term ranking the acidity or alkalinity of a substance or tissue. The body has a neutral pH, just slightly above 7. The skin is one exception: its pH on the surface is slightly acidic, at around 5.5. This acidity is necessary for the correct function of the epidermal metabolism. Very alkaline soaps (with a high pH) have harmful consequences: irritant effect, and damage to the skin's defense against infection. PH in normal skin is 6.5; in dry skin, it is inferior to 6.5.

  • Phenoxyethanol

    Phenoxyethanol is a preservative (see this term). As with all components of cosmetics and excipients in topical treatments, it is subject to very strict regulation. Phenoxyethanol has very low toxicity. However, following some studies, health authorities recently recommended not to use baby wipes containing phenoxyethanol in the name of total safety.

  • Phosphodiesterase

    An enzyme that plays a role in metabolizing cyclic AMP (see this term), an important molecule for cell function.  Phosphodiesterase inhibitors are currently undergoing clinical trials for treatment of asthma and atopic dermatitis.

  • Phospholipids

    Large lipidic molecules, present in cell membranes and in the lipidic layers surrounding corneocytes. They play a role in the barrier function and the skin's permeability. Anomalies in epidermal phospholipids (ceramides) have been observed in atopic dermatitis, and may play a role in the epidermal abnormality that is likely to be the cause of the condition. 

  • Photo-allergy

    Contact allergy aggravated by sun exposure. The most commonly known example is allergic reactions to fragrances: applying a perfume to which the subject is allergic followed by sun exposure causes redness followed by pigmentation to the affected area.

  • Photo-sensitivity

    An abnormal increase in sensitivity to the sun. This may be caused by certain conditions, or by taking certain medication. Photo-sensitivity is rarely increased in atopic dermatitis. In such cases, the term used is 'photo-aggravation' of atopic dermatitis.

  • Photo-tests

    Tests to measure sensitivity to the sun. An area of the back is exposed to specific amounts of UVA and UVB. Several techniques may be used depending on the clinical condition being evaluated. The most commonly used test is the MED measure, or Minimum Erythemal Dose. This tests the minimum quantity of UVB exposure to provoke redness (similar to sunburn). MED is expressed in joules per centimeter squared. It varies depending on the phototype (natural skin color) and for certain conditions (photo-dermatitis). These complicated tests are necessary only in rare cases.

  • Photo-therapy

    Treatment for certain skin conditions using ultra-violet radiation. This can involve UVA, UVB, shorter wavelengths, or both. A combination of UVA and an oral psoralene (a photo-sensitizing agent - increases sensitivity to UV) is known as PUVA therapy. PUVA therapy is an effective treatment for psoriasis and some other skin conditions. Photo-therapy may be indicated for atopic dermatitis in older children, adolescents and adults who have not been improved by more common treatments. UVB is most commonly used, or a combination of UVA and UVB. Photo-therapy is generally well tolerated but must be carefully supervised. All kinds of photo-therapy are medical treatments that require special equipment and are carried out by dermatologists. UV treatments used for esthetic results (such as sunbeds) are not medical and are not recommended. Exposure to UV increases the later risk of skin cancer, which is why it should only be carried out under medical control.

  • Pimecrolimus

    A drug that inhibits calcineurin, in the same family as tacrolimus. It is used in topical treatment for atopic dermatitis. For commercial and/or regulatory reasons, pimecrolimus is not sold in France. In other countries it is sold under the commercial name "Elidel".

  • Placebo

    Placebo is a Latin word meaning "I shall please". The placebo effect describes improvement to conditions or symptoms without any pharmacological cause, but purely by suggestion or psychological effect. A placebo is a tablet with no active ingredients, imitating the form of a drug. In chronic inflammatory dermatitis conditions such as atopic dermatitis, the placebo effect can be significant. Therefore before confirming that a treatment is effective, it must be proven to obtain better results than a placebo or "fake drug". The placebo effect requires that neither the patient nor his or her doctor knows that the drug being taken is not effective. This is the principle of therapeutic studies known as 'double blind'.


    The SCORAD rating (see this term) is the most commonly used technique for measuring the severity of atopic dermatitis. The scores are measured by a doctor. PO-SCORAD means SCORAD carried out by the patient themselves (Patient-Oriented). Using stock images and precise explanations, the patients, including even (older) children, are able to score the various symptoms of their atopic dermatitis (erythema, vesicles, etc.), as well as its spread, itching and impact on sleep. The PO-SCORAD has a double use. Firstly, it teaches patients to understand and be accurate when describing the symptoms of atopic dermatitis; and secondly, it can be carried out more frequently, for example once a week, and informs the doctor of the condition's development (flare-ups, remission, etc.) between consultations. The app to assess the severity of your eczema: PO-SCORAD

  • Pollinosis

    A respiratory allergy to pollen, the reproductive parts of certain plants (grass, birch, pine, etc.), which are transported in the air.  Pollinosis is also known as allergic rhinitis, or hay-fever, involving rhino-conjunctivitis or asthma. Pollen has a well-known geographical distribution and an exact seasonal pattern.  Eczema and respiratory allergies: two “cousins”

  • Pollution

    A general term to describe alterations to the environment caused by industrial activity, urban environments, traffic, etc. The role of pollution in skin diseases is likely minor, and impossible to prove.

  • Prebiotics

    Prebiotics are sugars used by probiotics (non-pathogenic intestinal bacteria) to grow.

  • Prednisone

    The chemical name for a derivative of cortisone used in oral corticosteroid therapy. (See general corticosteroid therapy)

  • Prevalence

    Number of individuals suffering from a certain disease at a given time in a given population.

  • Prick-tests

    Allergy tests whereby an allergen is introduced into the epidermis by pricking the skin with a special instrument. Tests by injection, whether using prick-tests or intradermal tests, are used in respiratory allergology. A positive test results in an itchy papule, which appears minutes after administration of the allergen.

  • Probiotics

    Probiotics are bacteria commonly found in the gut and considered to be beneficial for health. They are currently subject to study in various fields, above all in digestive diseases. Digestive bacteria have a role in establishing digestive immunity as well as general immunity. However, probiotic supplements (lactobacilla, bifidobacteria) have no significant effect on the development of atopic dermatitis.  The gut microbiome and eczema: how are probiotics beneficial?

  • Prostaglandins

    Lipidic molecules derived from arachidonic acid, which are involved in many of the body's functions, including inflammation. 

  • Protease

    Enzymes that degrade proteins. There are many proteases, and the consequences of their actions are varied. An excess of proteases has been observed in atopic dermatitis, which is responsible for breaking down certain important proteins for epidermal function, such as filaggrin.  

  • Pruritis

    Pruritis or itching is the main manifestation of atopic eczema. It disrupts sleep and causes scratching lesions.

  • Psoriasis

    Is a benign chronic skin disease, characterized by erythematosquamous lesions ... Psoriasis is frequent both in men and women ... Eczema versus psoriasis: how to tell the difference

  • Psychosomatic

    A term to describe the fact that many conditions have a significant psychological element, which may require specific management. Atopic dermatitis obviously influences the psyche, but this varies from patient to patient. It is common for psychological stress, family, school or professional problems to have an impact on the condition's development. However, indications for psychotherapy are rare.  Useful advices : Well being  

  • Psychotherapy

    Treatment by a psychologist. There are two types of psychotherapy: psycho-analysis and the techniques it inspires, and behavioral psychotherapy.  The psychological impact of atopic eczema is real

  • Pulpitis

    Dermatitis localized around the extremities of the fingers and toes, particularly in children. It can manifest as inflammation (for example atopic dermatitis or psoriasis) or infection (like impetigo).

  • Pustule

    A skin lesion that consists of a small blister filled with purulent liquid (pus). In atopic dermatitis, pustules indicate secondary infection, generally by staphylococci or streptococci (see impetiginization). It can also indicate herpes (see eczema herpeticum).

  • PUVA

    Photo-therapy technique (see this term) which combines exposure to UVA radiation preceded by taking a photo-sensitizing drug from the family of psoralenes. PUVA therapy is commonly used in treatment for psoriasis. 

  • Passive smoking

    Passive smoking describes the event of being exposed to cigarette smoke, and thus to its harmful consequences, without being a smoker oneself. An example of this would be children whose parents smoke. Passive smoking should especially be avoided for atopy sufferers, as it increases the risk of asthma.


  • Hydrotherapy treatment

    A stay at a hydrotherapy center, where water from a mineral source is used to treat certain conditions. In France, hydrotherapy treatments last three weeks and are reimbursed by social security. Atopic dermatitis is one of the dermatological conditions most commonly treated by hydrotherapy, both for children and adults. Hydrotherapy treatment for dermatological conditions combines water treatments (baths, showers), body wraps, controlled sun exposure, psychological support and information/education workshops. How does hydrotherapy help treat eczema?

  • Herpetiform dermatitis

    A fairly rare bullous auto-immune disease, typified by small bullae, with an easily recognizable appearance in biopsies, with deposits of IgA at the top of dermal papillae. Herpetiform dermatitis has no connection to atopic dermatitis.

  • Hand eczema

    Eczema appearing on the hands, and thus generally caused by a repeated exposure to a contact allergen, either due to professional activity or not. Learn more

  • Hanifin and Rajka

    Jon Hanifin (USA) and Georg Rajka (Norway) are two eminent dermatologists who are famous for their proposal of criteria to facilitate the diagnosis of atopic dermatitis in 1979. This is used in daily practice for difficult cases, and in clinical research to ensure that everyone is referring to the same condition. The "Hanifin and Rajka" criteria are commonly used by dermatological researchers.

  • Hapten

    An immunological term used to describe allergens with very low molecular mass. Allergens in contact eczema are generally haptens.

  • Heliotherapy

    Treatment employing exposure to natural sunlight. Whereas photo-therapy uses artificial ultraviolet light (UVA or UVB or both), sun therapy uses the sun's natural light, particularly at hydrotherapy or climate therapy centers. Atopic dermatitis is improved by heliotherapy and photo-therapy; this has been proven under medical control.

  • Herpes

    A viral disease, caused by a virus from the class herpesviridae, HSV-1 or HSV-2. There are several varieties of herpes: recurrent herpes of the face (cold-sores), genital herpes (a sexually transmitted disease), and severe herpes in some cases (in new-borns, immunosuppressed patients, etc.). Atopic dermatitis can expose patients to a severe form of herpes, known as eczema herpeticum (see term), which requires general antiviral treatment.  

  • Histamine

    A natural substance containing certain cells: basophils that are found in the blood, and mastocytes that are found in certain tissues including the skin. The release of histamine in the skin, caused by various stimuli, triggers an urticaria lesion (a raised red and itchy area on the surface). Anti-histamines (known as anti-H1 as they are specific to the H1-receptor for histamine) are effective against urticaria. However, they do not help atopic dermatitis, apart from to have a general calming effect.

  • Histiocytosis

    A disease caused by the proliferation of certain skin cells known as hystiocytes.

  • Homeopathy

    Homeopathy began in the 19th century, founded by Samuel Hahnemann. It is a medical system based on very different ideas to those of conventional medicine. Some people believe that it is able to change the way the body works, but there is no proof of its efficacy. In practice, homeopathic treatment alone cannot be relied upon to improve the symptoms of atopic dermatitis.

  • Hyper-IgE

    A syndrome involving a congenital immune deficiency, which causes sensitivity to certain infections and a higher level of IgE in the blood. This syndrome was described by Dr Rebecca Buckley, and is often known as Buckley syndrome, or Job syndrome. IgE levels are higher in atopic dermatitis, but not as high as in Hyper IgE.

  • Hyperpigmentation

    A darker tint to the skin, which can be a symptom of certain systemic conditions (Addison's disease, or adrenal insufficiency), or of certain skin conditions such as melasma. It may also result from prolonged inflammation, as seen in certain cases of atopic dermatitis.

  • Hypoallergenic

    That reduces the risks of allergies.

  • Hygienic hypothesis

    A hypothesis which states that allergies are caused by excessive hygiene at the start of life. Children who grow up in "clean", urban environments and have little contact with bacteria, often find their immune system becomes allergic and turn on their own bodies, rather than fighting real infections. The hygiene hypothesis gained some traction a few years ago. Certain medical writers believed that this explained the increase in allergies, including atopic dermatitis, in western countries. The hypothesis remains unproven. However, we should not believe that children must be exposed to infection in order to avoid allergies. Such an attitude has many disadvantages, and likely no real benefits.

  • Hay-fever

    A popular term used to designate rhinitis caused by pollen allergy (occasional rhinitis).

  • HLA system

    (Human Leukocyte Antigen) The main system for human histocompatibility, it is comprised of molecules carried by every cell in the organism, which are different from one person to the next (except in identical twins). The HLA system is important in two areas: Transplant medicine: a donor organ has much more chance of being accepted by the body if both donor and receiver have similar HLA systems; Vulnerability to certain diseases. Certain HLA groups are predisposed to certain diseases. For example, the HLA B27 group is prone to certain types of rheumatism.


  • Infantile seborrheic dermatitis

    A skin condition specifically affecting small infants (between 1 and 6 months) and often known as Leiner-Moussous disease. Infantile seborrheic dermatitis appears as redness on the buttocks and sometimes in skin folds, as well as particularly extensive and stubborn cradle cap. Local antiseptic treatment can result in rapid improvement. There is no link between infantile seborrheic dermatitis and atopic dermatitis.

  • Ichthyosiform erythroderma

    The name of a type of hereditary ichthyosis, where the skin is red and squamous all over the body. This appears from birth.

  • Immediate hypersensitivity

    A variety of allergy where the clinical symptoms appear very quickly (within minutes) after the introduction of an allergen. For example, allergy to insect stings or to certain drugs. Symptoms of immediate hypersensitivity are asthmatiform dyspnea (difficulty breathing), urticaria, and shock (known as anaphylactic shock)

  • Ichthyosis vulgaris

    Ichthyosis is a hereditary condition affecting keratinization (formation of the epidermis). There are several types of varying severity. The most common ichthyosis, also the least severe, is ichthyosis vulgaris (vulgar meaning frequent). It begins in childhood and is manifested through dry and scaly skin, particularly on the abdomen, arms and legs. It is often described as "lizard skin" or "snake skin". The term ichthyosis actually comes from the Greek word for fish. Ichthyosis vulgaris and atopic dermatitis often affect patients together. They have a similar genetic basis: a filaggrin deficiency. Emollient treatments are effective against Ichthyosis vulgaris.

  • IgE

    IgEs (immunoglobulins) are a type of antibody, manufactured by lymphocytes (white blood cells), most commonly in response to allergies or parasite infections. In atopic dermatitis, blood IgE is higher, but this is variable. Attempting to alter blood IgE levels, whether of total IgE or those specific to certain allergens, is not useful for treating atopic dermatitis.

  • Immunoglobulins

    A synonym of antibodies Antibodies are proteins known as globulins. Depending on their structure they are divided into classes: IgG, IgA, IgM, IgD and IgE. IgEs are involved in some allergies. The other classes have various functions, their primary role being to protect against infection.

  • Immunoglobulins E (IgE)

    IgE are the antibodies involved most specifically in allergic phenomena.

  • Impetiginization

    Secondary infection of a lesion that is initially not infected. For example, atopic eczema lesions can become infected by streptococci or staphylococci, and take on the appearance of impetigo. This is known as impetiginization, and requires anti-bacterial treatment.

  • Impetigo

    A bacterial infection, fairly common in children, which appears as small bullae (blisters) and yellowish crust. Impetigo often appears on the face. It is caused by streptococci or staphylococci, or a combination of both. Unless very minor, the treatment generally recommended is antibiotics for several days, as well as a topical treatment.

  • Immune system

    The mechanism that allows the body to fight infection and aggressions.


  • Visual analogy scale

    A simple line 10cm long, used to ask patients to rate the intensity of their pain or itching. 0 indicates no pain (or itching) and 10 represents the most intense pain (or itching) imaginable.  The app to assess the severity of your eczema: PO-SCORAD

  • Varioliform pustulosis

    See Kaposi-Juliusberg.

  • Vaccinations

    Vaccinations are effective protection against infectious diseases which in the past would have been serious or fatal, such as diphtheria, tetanus, and polio.It is essential that children get their vaccinations according to schedule, with jabs starting at around 3 months. Atopic children should be vaccinated  just like any other; eczema is not a contra-indication for any vaccine currently available.  The only exception is vaccination against smallpox (see this term), but this is no longer used.  Eczema and vaccines: should you avoid vaccinating your child?

  • Vaseline

    A fatty body created from petrol. Vaseline is a very effective and safe moisturizer, but not very pleasant to use. Its primary effect is to counteract dehydration of the epidermis by forming a 'film' on the surface. 

  • Vesicle

    A small raise area of skin filled with clear, yellowish liquid. Eczema, including atopic dermatitis, often involves vesicles. They are not always visible as they are very small, and because they are often broken by scratching. The weeping seen in eczema affected skin is from broken vesicles.

  • Vitiligo

    A common skin condition, typified by complete discoloration of the skin, which becomes completely white, with no other abnormalities. Vitiligo is difficult to treat. Phototherapy with UVB can be effective. The link between vitiligo and atopic dermatitis is a theoretical one, and has no real proof.   


  • Gel

    A galenic form that is more fluid than creams.

  • Glycerin

    Glycerin, or glycerol, is a simple lipid that is commonly used in cosmetics and topical treatments due to its hydrating properties.


  • Lymphocyte T

    A variety of lymphocyte with the fundamental role of providing delayed immunity (see delayed hypersensitivity) and cooperating with B lymphocytes which produce antibodies. There are many subsets of T lymphocytes, named after their surface markers (for example, T CD4+) or their role, (e.g. T-effectors, T-regulators). T lymphocytes that stimulate immune responses are known as T-helpers. It is likely that in atopic dermatitis there is some kind of imbalance in T-helper (TH) lymphocytes. TH2 lymphocytes dominate TH1 lymphocytes, which encourages the production of IgE. In fact, immune regulation in atopic dermatitis is a very complex field and not enough is currently known about it. Certainly, immune regulation disorders are not independent from epidermal abnormalities.


  • Quality of life

    Quality of life scales are questionnaires that attempt to evaluate the impact of chronic diseases on patients' daily life, psychological state, and social life (professional, hobbies, etc.). The general aim is to find out what really affects individual well-being and social life, and thus affects the patients themselves, and not just the clinical and biological symptoms that doctors are commonly interested in. Impact on quality of life is often parallel with the condition's severity, but this is not always the case. In fact, some conditions which may appear benign can have a serious impact on patients' personal and social life. It is also important to ensure that treatment improves the patient's quality of life.


  • RAST

    Radio-Allergo-Sorbent Test. An immunological technique used (among others) to measure the level of total IgE in the blood.

  • Rhinitis

    Inflammation of nasal mucous membranes.  Within atopy, some types of rhinitis are infectious (such as the cold virus), and others are allergic. Eczema and respiratory allergies: two “cousins”

  • Rhino-conjunctivitis

    An allergic condition of the nasal mucous membranes and conjunctiva. The primary cause is allergies.  Rhino-conjunctivitis caused by pollen allergies (hay-fever) are occasional, and appear only at certain times. 


  • Ultraviolet

    Part of the electromagnetic spectrum just below visible light. Ultraviolet waves have significant biological actions. They are:  UVB, with a wavelength between 280 and 320nm. These are primarily responsible for sun burn (acute phototoxicity). UVA, with a wavelength between 320 and 400nm. They do not burn, but are responsible for photosensitivity.  This distinction is useful in fundamental photobiology, and for certain treatments using ultraviolet light (phototherapy). In practice one should protect oneself from all kinds of UV in order to avoid skin aging and cancer in the long term. This is the role of currently-available photoprotection products. 

  • Urea

    A small molecule that is naturally derived from protein metabolism. Urea is part of epidermal NMF. It is used in dermo-cosmetics. In low concentrations it is hydrating. In higher concentrations it is keratolytic and irritant.  

  • Urticaria

    Comes from the Latin 'urtica' meaning nettle. Urticaria is a common skin reaction that appears as papules or raised red areas of various sizes. They are very itchy. They are temporary, lasting only a few hours, although they reappear elsewhere. It is important to determine the cause of urticaria lesions. It could be due to a drug, a food, or another cause. Whilst urticaria involves similar immunological mechanisms to those involved in atopic conditions, it is not very common in atopic patients.

  • UVA

    See Ultraviolet.

  • UVB

    See Ultraviolet.


  • Warts

    Small benign tumors caused by the papilloma virus. Warts on the fingers are common in young children. They do not affect atopic patients differently to others. 

  • Wiskott-Aldrich

    A rare genetic disease combining severe eczema similar to atopic dermatitis with a blood platelet deficiency, causing excessive bleeding and vulnerability to infection. 


  • Xerosis

    Skin dryness. Xerosis of the skin is the sign of an epidermal dysfunction that favors itching and the penetration of germs and allergens.