Frequency of systematic reactions to penicillin skin tests

Background: Penicillin skin testing is generally considered to be safe when performed sequentially with puncture and intradermal testing although fatalities have been reported. Objective: We analyzed the rate of systemic reactions to penicillin skin tests for a period of seven and two-thirds years. Method: This retrospective study used a computerized database at the Mayo Clinic. Altogether 1710 patients were skin-tested to penicillin from January 1992 to September 1999. All patients tested had a history of penicillin allergy. Patients were tested with benzylpenicilloyl polylysine (Pre-Pen) (6.0 X 10(-5) M), freshly prepared penicillin G (10,000 units/ml), and penicilloate (0.01M). Prick tests were done first and if negative then intradermal tests. Systemic reactions were evaluated and treated by physicians. Results: Eighty-six patients had positive penicillin skin tests of which two had systemic reactions. Our systemic reaction rate for all patients tested was 0.12%; and 2.3% for the penicillin skin test-positive group, with no fatalities. Conclusion: The incidence of systemic reaction to penicillin skin tests is low. Skin prick tests should always be done first. If there is a history of a previous serious reaction, the skin tests-if done-should be diluted to start with. Those doing penicillin skin tests should be prepared to treat a systemic reaction.