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What is an IgE-mediated allergy?

Allergy is classically defined as an exaggerated, pathological, specific immunologic reaction to foreign (exogenous) substances.

As the body of evidence in immunology and immunopathology grows, the term ‘allergy’ is increasingly being confined to denote type I hypersensitivity reactions. However, there is as yet no consensus about definitions. In a somewhat narrower sense, allergy is defined as a condition triggered by a specific, acquired immune response to a harmless, non-pathogenic antigen.

The allergic reaction results from the production of specific IgE antibodies directed against innocuous and typically widespread antigens. An antigen in this type of hypersensitivity reaction is called an ‘allergen’.

The most important allergens include airborne allergens such as grass, tree or weed pollen, as well as moulds (or rather their spores), which are mainly released in summer and autumn. Patients often show cross-reactions to foods, the so called pollen-associated food allergy or oral allergy syndrome (OAS).

The spectrum of perennial allergens includes mainly house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae, and cat allergens. Less frequent are perennial reactions to other furry animals and moulds [1].

This means that an allergen is a non-infectious agent that triggers an IgE antibody response and hence a type I hypersensitivity reaction [2]. Type I reactions are the classical immediate reactions that occur seconds to minutes after allergen exposure. They include the pattern of symptoms seen in allergic rhinitis and conjunctivitis, allergic asthma, urticaria, and food and insect venom allergies. Anaphylaxis is considered the most severe form of an acute allergic immediate reaction and, in a narrower sense, is typically IgE-mediated [1].

Read more on the next page: "Allergy - Pathomechanisms"

[1] Ring J. Angewandte Allergologie. 3., neu bearbeitete ed. München: Urban & Vogel Medien und Medizin Verlagsgesellschaft mbH & Co. KG; 2004.
[2] Schultze-Werninghaus G, Fuchs T, Bachert C, Wahn U. Manuale allergologicum. München - Orlando: Dustri-Verlag Dr. Karl Feistle GmbH & Co. KG; 2004.

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