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Allergy

The definition of an allergy is: an abnormal immunoreaction, brought by IgE antibodies, and liberating mediators (immunologic, histamine) in a given organ (nose, eyes, bronchus, skin or digestive system) when the patient is exposed again to an allergen.Immediate allergic reaction (IgE), anaphylaxyAcute reactions are induced by the IgE (synthetizing B lymphocytes) and occur only minutes after the contact.Seriousness of the reaction depends on the organ and the degree of sensitivity. For instance, rhinitis or conjunctivitis may be caused by contact with pollens or cat dander, but they can also cause violent asthma. Acute urticaria is also a possible immediate allergic reaction.Serious reactions are characterised by anaphylactic shock (dyspnoea, fainting), typical in case of hymenoptera venom (bee, wasp), food allergy, or specific medication (i.e. penicillin).Delayed allergic reactions (cellular)Delayed reations are induced by T lymphocyte (immunity cells) and macrophage (antibody). Characteristic lesions are contact dermatitis. IgE have no part in the process. Although tiresome, these lesions are not dangerous. They usually appear  slowly (over a few days).

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