Penicillin skin testing in advance of need: Multiyear follow-up in 568 test result-negative subjects exposed to oral penicillins

Background: There are few published data on adverse drug reactions and/or resensitization associated with oral penicillin use in penicillin allergy history-positive/penicillin skin test-negative individuals during routine clinical care with multiyear follow-up. Objectives: We sought to provide long-term follow-up data on the type, severity, and frequency of adverse reactions associated with oral penicillin use in individuals who have histories of penicillin "allergy" yet also have negative results on penicillin skin tests done in advance of need. We also aimed to repeat testing on individuals with penicillin-associated adverse reactions. Methods: Medical records were reviewed for penicillin use and associated adverse reactions in all 568 penicillin skin test-negative individuals who had received at least 1 course of oral penicillin after testing but before December 31, 2001, during routine care. These individuals were drawn from a group of 1246 penicillin skin test-negative individuals seen initially between November 16, 1994, and August 13, 2001. Results: The mean length of follow-up was 4.26 +/- 1.64 years (range, 0.39-7.12 years). The mean penicillin exposure was 3.94 +/- 3.91 courses (range, 1-22 courses). Only 65 (11.4%) of 568 subjects had any penicillin-associated reactions, and 6 subjects had 2 reactions each. A reaction occurred in 27 subjects (4.8%) with their first penicillin reexposure. There were 71 (3.2%) reactions with 2236 total penicillin courses. There were no serious reactions. Repeated testing was done in 33 subjects older than age 18 years. Only 1 subject was positive on repeated penicillin skin testing. Conclusion: Penicillin use after negative penicillin skin testing done in advance of need is safe, and resensitization is rare.