Treating Patients With a History of Non-Life Threatening Allergic Reaction to Penicillin With Penicillin: Is It Safe?

To examine whether oral challenge with penicillin for patients with a known history of non-life threatening allergic reaction to penicillin is well-tolerated irrespective of skin-testing results long after the event occurred.

Methods: In this prospective, open-label, controlled, multi-clinical trial, 8702 individuals from primary care clinics were screened for penicillin allergy. 169 patients with a history of non-life threatening allergic reaction to penicillin, dating back at least 3 years, were recruited for study. Regardless of the response to penicillin skin testing, patients received the recommended daily dosage of penicillin and amoxicillin on two separate occasions. 2-6 years later a follow-up was conducted to assess the outcomes of further penicillin administration.

Results: 92.9% of the patients had an allergic reaction 6 years or longer before enrollment in the study. Of 272 challenges, 137 were skin-test positive with mild rash in 9 patients (6.6%), and 135 were skin-test negative with similar allergic reaction in 5 (3.7%) (P =.29). At follow-up, 3 of 55 patients (5.5%) who were given a full treatment course of penicillin developed mild skin eruption.

Conclusions: A positive penicillin skin testing of patients with a history of non-life threatening allergic reaction to penicillin occurring 3 years or longer from the event was not associated with a greater prevalence of adverse reactions to oral challenge with penicillin than a negative one. It is of importance to determine whether oral challenge can serve as a diagnostic procedure for this particular group of patients, thereby saving the need for prior penicillin skin testing.