penicillin allergy
Last reviewed 09/2023
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