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Penicillin allergy

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Penicillin allergy occurs in 1-10% of patients taking the drug. However life-threatening problems are rare - anaphylaxis occurs in about 15-40/100,000 treated patients. A fatal outcome occurs in about 1.5-2/100,000 treated patients.

Reactions can be divided in four immunological groups:

  • type I reactions - IgE mediated immediate hypersensitivity e.g. urticaria, anaphylactic shock
  • type II reactions - antibody reactions with antigens on cell surfaces e.g. Coomb's positive haemolytic anaemia
  • type III reactions - immune complex mediated e.g. serum sickness, drug-associated fever
  • type IV - delayed cell-mediated reactions e.g. contact dermatitis

A history of allergy does not predispose a patient to the development of penicillin allergy. However if an anphylactic reaction develops in an atopic patient then it is likely to be more severe.

Reference:

  • Drug and Therapeutics Bulletin (1996), 34 (11), 87-88

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