Outpatient Study Highlights Effectiveness of Penicillin Allergy Delabeling via Oral Challenge

A retrospective chart review conducted at an outpatient allergy clinic found that oral drug challenges are safe and highly effective for penicillin (PCN) allergy delabeling, reinforcing their clinical utility in addressing a widespread source of diagnostic inaccuracy and suboptimal antibiotic use.

These results were presented at the American College of Allergy, Asthma & Immunology 2025 Annual Scientific Meeting.

Among 222 patients referred for drug allergy evaluation between November 1, 2022, and August 31, 2023, 196 (88.3%) carried a documented PCN allergy label. Of those, 23 patients (11.7%) were de-labeled based on historical data alone.

An additional 66 patients (33.6%) completed a graded oral penicillin challenge. Of those, 98.5% were safely delabeled. “Our study provides further evidence that oral drug challenges are safe and effective at de-labeling penicillin allergy,” the authors reported.

Despite the success rate, 93 patients (47.4%) did not return for their recommended oral challenge during the study period, highlighting a major barrier to broader implementation. Only 13 patients (6.6%) remained labeled as allergic following evaluation—due to serum sickness–like reactions (n=9), positive PCN skin tests (n=2), or relabeling at an outside facility (n=2).

Given that up to 95% of patients labeled with a PCN allergy are not truly allergic, mislabeling carries clinical and economic consequences. These include unnecessary broad-spectrum antibiotic use, higher rates of adverse drug events, and increased healthcare costs.

The study team is now exploring solutions to improve follow-up rates. “Next steps in the project include developing opportunities to overcome barriers preventing the completion of oral drug challenges at subsequent visits,” they noted.

These findings support broader adoption of structured allergy assessments and oral challenges as key tools in antimicrobial stewardship and patient safety.

Reference
Retrospective review of penicillin allergy evaluations and subsequent de-labeling: A single pediatric tertiary center experience. Presented at: American College of Allergy, Asthma & Immunology 2025 Annual Scientific Meeting; November 6-10, 2025; Orlando, FL