Penicillin anaphylaxis: a review of sensitization, treatment, and prevention.

Penicillin and its derivatives are the commonest cause of drug-induced anaphylaxis, accounting for some 500 deaths per year in the United States. Penicillins are, however, sometimes withheld unnecessarily in patients who give spurious histories of penicillin allergy. A properly performed skin test will detect patients at risk of serious anaphylaxis. Many physicians do not fully appreciate the value of penicillin skin testing, however, and this has contributed to the withholding of penicillin and the use of other, often more expensive medications. Skin testing with a mixture of benzylpenicilloyl polylysine (major determinant) and a minor determinant mixture detects all patients at risk of major anaphylaxis. Of patients who test negative with these reagents, 1% to 4% will have non-life-threatening urticarial reactions. Skin testing is most useful in patients with a vague or inconsistent history of penicillin allergy for whom alternative antibiotics would not be effective or convenient. Aztreonam is the only semisynthetic penicillin that may safely be used in penicillin-allergic patients. Desensitization may be attempted in the patient with a positive skin test for whom there is no alternative to a penicillin-type drug.