Different allergens trigger four mechanisms and symptoms. The reactions can occur immediately or with a delay.

Immediate-type allergy (Type I)

In this type, the symptoms occur immediately or within a few minutes. They usually affect the skin or mucous membranes. The immediate type is the most common form of allergy, as in pollen allergy, food allergy, allergy to animals or to insect venom.

Type II allergy

This is a very rare form of allergy. Blood cells may become damaged. Medicines, for example, are possible triggers of Type II allergy.

Type III allergy

This often plays a key role in drug allergy. Antibodies are directed against foreign substances (antigens) that are dissolved in the blood. This gives rise to larger complexes which are deposited on the walls of the small blood vessels, e.g. in the skin or the kidneys, where they trigger an inflammatory reaction.

Delayed-type allergies (Type IV)

This is a late allergic reaction. It is the only form of allergy in which the sensitised defence cells (T-lymphocytes) act directly against allergens. In most cases, Type IV allergens are not large molecules, such as proteins, but metals or simpler chemicals. Type IV allergies appear, for instance, in the form of contact eczema, e.g. to nickel in fashion jewellery or fragrances in perfumes.

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

aha! Swiss Allergy Centre helps

  • aha!shop: Booklets and factsheets provides detailed information and are available in German, French, Italian.  The booklet "Allergies – simple to explain" and the questionnaire "Do I have an allergy" is available in English
  • Experts on the aha!infoline will be happy to answer personal queries: Monday to Friday, 08.30–12.00.
  • Products and services awarded the Allergy Seal of Quality – an added benefit for sufferers.
  • aha!kinderlager for children with allergies aged between 8 and 12 years: holidays full of variety with lots of sports, play and fitness. Under expert supervision, children learn to deal better with their allergies and/or asthma.
  • aha!jugendcamp for youngsters aged between 13 and 16 years: a broad range of sports and leisure activities, skilled leaders tackle aspects of allergic diseases in adolescence.
  • Education and courses on the subjects "Allergy, asthma, chronic bronchitis", "Anaphylaxis" and "Neurodermatitis"
  • We value your opinion. Or would you like to exchange experiences with other sufferers? Find out more under "Beratung und Austausch"
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