© by aha! Swiss Allergy Centre - Info on allergies - Glossary - a little girl with an encyclopedia

What is meant by atopy, what is sensitization or progression? Important facts, connections and technical terms from the area of allergology.


Complete elimination of certain foods, for instance. In allergology, abstinence also means: avoiding contact with the allergen and giving up pets or plants, for instance.

Adrenaline prefilled syringe (EpiPen) / Emergency kit

Patients with severe generalised allergic reactions to insect stings (grade III or IV, see also anaphylactic shock), during the flight time of hymenoptera (including bees, wasps, bumblebees), should carry an adrenaline auto-injector and emergency tablets. Sufferers have to receive instructions on the use of these medicines verbally and in writing. The handling and shelf life of the auto-injector should be checked regularly.


An allergen is a substance that is harmless in itself but can trigger hypersensitivity reactions mediated via the immune system. Allergens are mostly proteins.

Allergic march

If allergic diseases start as early as infancy and childhood, then follow a characteristic pattern, this is known as the allergic march (or atopic march). It defines the situation where children with an allergic predisposition "grow out" of one allergic disease as they get older, but then start to suffer from a subsequent form of allergy. Furthermore, hay fever can develop into asthma, which professionals refer to as progression.


Exaggerated reaction of the immune system to substances that are foreign to the body but harmless in themselves, or to substances such as pollen or foods. To date the reasons for this have still not been fully explained.

Allergy prevention

Prevention refers to measures that reduce the risk factors in people with a family predisposition. Recent scientific findings indicate that too much prevention through strict hygiene in infancy has a rather counterproductive effect. Secondary prevention means early detection of the start of an allergy and prevention of an allergic march with the right treatment. Tertiary prevention involves avoiding the relevant triggers in the case of pre-existing allergies.

Allergy test

If an allergy is suspected, an allergy test can be done to identify or rule out a specific allergen. Allergy tests can be divided into skin tests, blood tests and provocation (or challenge) tests.

Anaphylactic shock (anaphylaxis, allergic shock)

Anaphylactic reactions can be subdivided into five stages depending on their severity. Treatment is adapted to the stage in question.

Local reaction (stage 0)

Excessive, local swelling/redness of the injection site. Treatment: cool the area, if need be take antihistamine tablets.

Mild generalised reaction (stage I)

Generalised reddening of the skin, skin blotches, urticaria and itching, especially on the palms and the soles of the feet as well as mucosal reactions with itchy nose, urge to sneeze, runny nose, watering and itchy eyes, restlessness or headache. Treatment: antihistamines, monitoring of blood pressure and pulse and, if necessary, cortisone injection.

More severe generalised reaction (stage II)

Blood pressure and pulse changes, shortness of breath (mild dyspnoea, onset of bronchospasm), urge to defaecate or urinate, feelings of anxiety. Treatment: urgently consult an emergency doctor because the person concerned must be kept under observation. Inhalation with asthma drugs or adrenaline, infusion and cortisone.

Severe generalised reaction (stage III)

This is a rare occurrence but within a matter of seconds after a sting or an injection it can lead to shock (blood pressure decrease, pallor, bronchospasm with ominous dyspnoea, clouding or loss of consciousness, possibly involuntary loss of stool or urine). Treatment: as in stage II but at a higher dosage.

Vital organ failure (stage IV)

Clearly evident failure of vital functions (respiratory / cardiovascular arrest). Treatment: Resuscitation (intubation, ventilation, external cardiac massage).

Anti-allergic agent

Medication that gets rid of or at least relieves the symptoms of an allergic disease. This often means antihistamines.


Also known as histamine receptor blockers. They contain substances which weaken or neutralise the effect of the body’s own messenger histamine by blocking the histamine receptors. Antihistamines are used especially for the treatment of allergies.

Asthma attack

In an asthma attack the airways narrow so severely that breathing out causes considerable strain. Sufferers feel as if they are not getting enough air, which can make them feel anxious. Typical signs of an asthma attack are the use of auxiliary respiratory muscles (shoulders lifted) and wheezing.

Atopy (predisposition)

 Personal or family predisposition to produce antibodies after contact with small amounts of allergens. Atopy denotes the tendency to react to contact with harmless substances with immediate-type allergic symptoms (type I allergy). Atopy is a term for the body’s tendency to the increased formation of immunoglobulin E antibodies (IgE).

Blood test: RAST (radioallergosorbent test), CAP test (cellulose-absorbed phase)

The laboratory result is available about a week after the blood sample is collected. Blood tests can be done even on newborn babies. IgE class antibodies to allergens are detected. Blood is screened for specific allergens which are suspected of triggering a specific allergy. The probability of an allergy rises with elevated RAST values. A definite diagnosis can only be made when blood test and symptoms are matched. RAST is often used as a means of monitoring the progress of an allergy. The CAP test is comparable to RAST, but is being used more and more frequently.


Bumblebees are larger, heavier and hairier than honey-bees, but belong to the same family. The stinger of a bumblebee has no barbs and will not stay put. Bumblebees are very docile and only sting if they feel threatened. If they fear an attack on their nest, they lie on their backs buzzing threateningly. The very rare attacks with bites and stings may trigger allergic reactions. The venom of bumblebees and other bees is similar. However, bumblebee venom and not bee venom is always used for desensitisation of a severe bumblebee venom allergy.

Calcineurin inhibitors / Immunomodulators

Immunomodulators are active ingredients in medicines which have an influence on the immune system. They include the active substances tacrolimus and pimecrolimus, which are calcineurin inhibitors. They are used to treat atopic dermatitis (neurodermatitis) as an ointment or cream applied topically to the skin where they have an anti-inflammatory effect and relieve itching.


Cortisone and cortisone products (derivatives) have been used for decades. The very high doses used in the past caused a lot of side effects. Nowadays new cortisone drugs (known as corticosteroids) are in use. They make it possible to finely tune the dosage. Side effects are largely avoidable if the drugs are used properly, especially with the topical or local use of ointment, nasal or asthma sprays. Owing to their anti-inflammatory and anti-allergic effects, cortisone drugs are often indispensable in the treatment of severe allergic diseases of the airways and the skin.

Cross-reaction (cross-allergy)

In a cross-reaction, the body is unable to distinguish similar proteins (allergens). As well as their first allergy, such as allergy to birch pollen, allergy sufferers usually react suddenly to one or two foods and to a different pollen.

Desensitisation (specific immunotherapy, hyposensitisation)

Desensitisation is a causal therapy for IgE-mediated Type I allergies. It is often carried out in cases of allergy symptoms connected with pollen allergies, house dust mite allergy, exceptionally in animal and mould allergies. Desensitisation therapy should be recommended for severe insect venom allergies (bee and wasp venom) because it protects against life-threatening reactions. The allergens are injected under the skin in ascending doses (SCIT – subcutaneous immunotherapy) or administered as tablets or drops (SLIT – sublingual immunotherapy). The aim is to get the body used to the allergen and build up immunological protection that will prevent further allergic reactions.
Successful desensitisation aims to reduce or completely eradicate symptoms.

Diagnostics in food allergies

When food intolerance is suspected, finding the cause is complex. Ideally this is done through cooperation between the sufferer, a nutritionist with allergy experience and a specialist.

Elimination diet (diagnostic diet)

Over a limited period the "suspicious" food is left out of the diet. This diet should be followed strictly for two to four weeks. If the symptoms have not disappeared or have not been appreciably relieved after that period, the omitted foods can in all probability be excluded as a trigger. If the sufferer becomes symptom-free on the diet, this points to the suspected allergen. A provocation test can be performed to confirm the diagnosis.

Emergency kit

With or without an adrenaline syringe. All patients who have a generalised allergic reaction (shock) should carry an adrenaline auto-injector (EpiPen®/Anapen®/Jext® 0.3 mg) and emergency tablets (e.g. 2 x 10 mg cetirizine and 2 x 50 mg prednisone). Sufferers have to receive verbal and written instructions on the use of these medicines in the event of renewed contact with the allergen. The handling and shelf life of the auto-injector should be checked regularly.

Emergency medical ID (Allergy card)

The Swiss Society for Allergology and Immunology (SGAI) provides doctors and pharmacists with allergy ID cards. They hand out the completed ID cards to allergy sufferers. The allergy ID card is a document that is issued after competent diagnosis and available in German, French and Italian, always combined with English. The allergy cards for medical practices, hospitals, clinics, pharmacies and healthcare professionals.

Encasing: (mite-proof covers)

Mattresses, pillows and duvets are encased in covers made of very closely woven fabric. Mites are unable to penetrate this fabric. In addition, bedding should be washed once a week at a temperature of at least 60°C. Information about mite-proof covers (encasings) with the Swiss allergy label can be found at www.service-allergie-suisse.ch.


Enzymes are proteins  that trigger biochemical reactions. Enzymes have important functions in the metabolism. They control the greater part of digestion (Verdauung). Enzymes are substances that trigger a chemical reaction (digestion).

Food incompatibility

The collective term of incompatibility covers all reactions that reappear whenever a certain food is consumed. A distinction is drawn between hyper-reactions with allergic and non-allergic symptoms, food poisoning, malabsorption, enzyme deficiencies or psychosomatic reactions (e.g. aversions).

Food intolerance

This collective term covers four types of reaction:

  • Toxic reactions: poisonings (e.g. fungus poisoning)
  • Intolerance reactions: Enzyme deficiency (e.g. lactose intolerance)
  • Allergic reactions: immune-mediated reactions
  • Pseudoallergic reactions: reactions to foods that contain or liberate histamine (e.g. certain cheese, fish or wines).

More than 20% of the population in industrialised countries suffer from some form of food intolerance.


This is a hormone-like, vital substance. In normal circumstances, the enzyme diamine oxidase from the intestinal mucosa leads to rapid breakdown of histamine.

Histamine intolerance

The clinical picture of histamine intolerance resembles that of food allergy because in both cases the symptoms are mediated by histamine. No IgE antibodies to food ingredients are formed and no previous sensitisation is required. The reactions occur whenever the person is in contact with histamine. Foods with a particularly high histamine content: mature cheese, smoked fish and sausage goods. Red wine also contains a lot of histamine.


History-taking refers to the initial discussion between patient and attending physician. It covers a patient’s history of disease based on personal experience. History-taking makes it possible to reach a diagnosis. As a rule, the history-taking is carried out before or not later than during the medical examination.


The venom of hornets is similar to that of wasps. The sting is more painful because the stinger is longer and penetrates more deeply. Hornets are very peaceable, stings are rare and are seldom raised as an issue in relation to allergies.


Collective term for various species of insects such as bees, bumblebees, wasps, hornets or ants. There are over 115,000 known species of hymenoptera, around 11,500 of those in Europe alone. Hymenoptera can trigger allergies with their venomous stings, which can lead to anaphylaxis (anaphylactic shock). Allergy to ant venom is extremely rare in our part of the world.

Immunoglobulin E (IgE), IgE antibody

IgE is found in minute concentrations in the serum. Raised IgE levels are caused by complex genetic factors but also by environmental influences. High IgE levels are observed mainly in atopic diseases and worm infections. Even though a low IgE level does not rule out an allergy and very high IgE levels can also be present in clinically healthy people, the following rules apply: the higher the IgE concentration, the more probable an atopic disease.

Immunoglobulin G (IgG), IgG antibody

Antibodies which act against microbes such as bacteria and particularly viruses. IgG antibodies against foods reflect a normal immune response and should not be classified as disease-causing in terms of food allergy or intolerance. Dietary recommendations and therapeutic measures based on IgG measurements should therefore be rejected. National and European allergology associations unanimously advise against IgG diagnostics with foods. Nevertheless suppliers manage to publicise these tests which are often expensive but are nonsensical from an allergology point of view.

Immune response

Reaction of the immune system to foreign organisms or substances. The immune system is able to react to foreign organisms (bacteria, viruses, fungi, parasites). If the irritant is classified as non-hazardous, it will not trigger any reaction in the future (immune tolerance). However, substances from the environment that are harmless in themselves may mistakenly be classed as dangerous and trigger a reaction (allergy). In the context of immunotherapy, immune response means  the development of tolerance to an allergen.


Immunology is the study of the biological principles of the body’s defence against disease-causing organisms and other substances that are foreign to the body (toxins). It also covers disruptions and dysfunction of these defensive mechanisms. There are various areas of immunology. Clinical immunology examines disturbances of the immune system as they occur in allergies.


aha! offers further training seminars on the subject of allergies for nutritionists. Allergy sufferers can find suitably qualified HF/FH nutritionists listed (in german) on the website of aha! Swiss Allergy Centre.


In cases of malabsorption, the intestinal tract is not able to absorb enough nutrients into the bloodstream and lymph ducts because of a disorder.

Mast Cells

Mast cells are defensive cells of the immune system and distributed throughout the skin and the mucous membranes, close to blood vessels and in the organs. One of the substances they release is histamine, which increases vessel permeability and can result in blood plasma escaping into body tissues. This leads to angioedema or wheals.


Progression refers to allergic reactions moving from the upper airways (nasopharynx) to the lower airways (bronchi, lungs): from allergic rhinitis to bronchial asthma. Just under half of pollen allergy sufferers will also suffer from asthma at some time. Desensitisation is recommended to prevent this progression (see Allergic march).

Provocation test

In a provocation (or challenge) test, the allergen solution is applied to the mucous membranes of eyes and nose. It may also be inhaled or administered by direct contact with the skin/mucous membrane. Provocation tests are performed under strict medical supervision (hospital) and the allergic symptoms are triggered in a controlled way.


A pseudoallergic reaction is an intolerance reaction which very closely resembles a classic allergic reaction ("immediate-type") without an immunological reaction being detectable in the blood. The most common triggers are medicines and food additives. "Pseudoallergens" are substances/mediators (e.g. histamine) which do not affect the immune system.


If sensitisation exists, it means the body has built up a misdirected, specific immune response after first contact with a foreign substance (often an Allergen). On renewed contact, an allergic reaction may ensue. Sensitisation can usually be detected by means of a skin test. Not every sensitisation will cause symptoms. If symptoms arise, for which an allergen is suspected as the cause but no sensitisation can be detected, this is referred to as intolerance. An allergy may only be assumed if sensitisation is followed by symptoms of the skin, gastrointestinal tract, respiratory tract or circulatory system.

Skin test

Allergen solutions are dropped onto the skin of the forearm or the back and pricked with a fine needle under the skin (prick test). If the allergen causes a reaction after 20 minutes similar to that following a mosquito bite, the test is positive. Skin tests are routinely performed by trained personnel. The allergen may also be applied using a patch. However, then the reaction can only be assessed after 1–2 days.

SOS capsule

The capsule contains a mini-emergency medical ID in 6 languages which contains the most important personal and medical details. This information is helpful and significant for emergency physicians and paramedics. SOS security capsules can be worn on a neck chain, a watch strap, a bracelet or a key ring.

Specific immunotherapy (SIT)

The aim of this therapy is to accustom the body slowly to the allergy-causing substance. The immune system is confronted repeatedly with the allergen at defined intervals. The therapy lasts 3–5 years. Further information on the subject is given in the booklet "Specific immunotherapy" (look for under aha!shop German, French, Italian).


In allergology, triggers refer to factors that induce allergy symptoms. They are not allergens (proteins), but additives or irritants (e.g. perfumes). Even the cold can act as a trigger.


Also known as nettle rash. This involves swelling of the skin (wheals) and redness of the skin. In urticaria, wheals can form or disappear again within a matter of minutes. Further information on the subject is given in the booklet "Urticaria – nettle rash" (look for under aha!shop German, French, Italian).

Winter feet

The appearance of dry, itchy and scaly skin changes on the anterior part of the foot, especially during the cold season and often in children aged between two and ten years, can be referred to as atopic winter feet. A specialist needs to carry out the differential diagnosis and distinguish atopic winter feet from, say, athlete’s foot or contact allergy.


Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.