Skin tests in the investigation of penicillin allergy

Allergy to penicillin is reported to occur in up to 8% of the patients who receive this class of drugs. 80 to 85% of the patients with a positive clinical history to penicillin will nevertheless tolerate penicillin with no adverse effect. Of the remaining 15 to 20%, only a few will develop a severe adverse reaction, and these patients can be identified by skin tests with derivatives of penicillin used at optimal concentrations according to a protocol that is effective and safe. Skin tests to penicillin are positive in 25% of patients with a history of an immediate reaction to penicillin; they are more frequently positive in those who have had a severe reaction. In addition to being able to identify patients who are at risk for a severe reaction when they take penicillin, skin tests can also provide immunological evidence of the origin of delayed clinical reactions such as maculopapular rashes. Such rashes, a frequent and benign manifestation of penicillin allergy, are usually caused by the widely used aminopenicillins. Intradermal skin tests (IDR) and late phase (patch) tests can demonstrate allergy to betalactamines in 5 to 45% of patients with negative skin tests to major and minor determinants of penicillin. When skin tests are positive, provocation tests are not recommended. On the other hand, when the skin tests are negative, an oral provocation test should be done, but such tests can result in an immediate clinical reaction, which may be severe in 3 to 10% of cases. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.