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Etymology: Gk, ana, up, phylaxis, protection
an immediate, systemic hypersensitivity reaction to an exogenous antigen mediated by immunoglobulin E or G. It can be triggered by many substances, including drugs, especially penicillin and other antibiotics; foreign proteins used as therapeutic agents such as insulin, vaccines, allergen extracts, and muscle relaxants; insect venom, especially from bees, wasps, hornets, and fire ants; and certain foods such as shellfish, berries, chocolate, eggs, and nuts. Also called type I hypersensitivity. Compare cell-mediated immune response, cytotoxic anaphylaxis, immunocomplex hypersensitivity. See also anaphylactic shock.