Type I IgE-mediated hypersensitivity reaction. Release of histamine and other agents causes: capillary leak; wheeze; cyanosis; oedema (larynx, lids, tongue, lips); urticaria. More common in atopic individuals. An anaphylactoid reaction results from direct release of mediators from inflammatory cells, without involving antibodies, usually in response to a drug, eg acetylcysteine.
Common precipitants
Drugs, eg penicillin, and contrast media in radiology
Latex
Stings, eggs, fish, peanuts, strawberries, semen
Signs and symptoms
Itching, erythema, urticaria, oedema
Wheeze, laryngeal obstruction, cyanosis
Tachycardia, hypotension
