De-labelling Penicillin Allergy in Paediatric Patients Using Oral Challenge: A Retrospective Study from Northwestern Ontario

Purpose: To find out how many children labelled as allergic to amoxicillin are truly allergic, and to assess whether a direct oral amoxicillin challenge, without prior skin testing, is a safe and effective way to remove incorrect allergy labels in low-risk pediatric patients in Northwestern Ontario. Methods: We conducted a retrospective review of pediatric patients (6 months-15 years) referred for suspected amoxicillin allergy at two Northwestern Ontario hospitals between 2015 and 2025. Eligible patients underwent oral amoxicillin challenge. Clinical data were summarized, and group comparisons were performed using Fisher’s exact and Wilcoxon tests. Results: Of 96 patients, 93 (96.9%) tolerated the oral amoxicillin challenge, while 3 (3.1%) developed mild, delayed rashes. Notably, all three had previously reported delayed reactions (5-10 days) after their initial amoxicillin exposure, and two reproduced the same rash type following the challenge. This reproducibility suggests that the timing and nature of index reactions may help predict outcomes during oral challenge. Conclusion: The prevalence of true penicillin allergy among paediatric patients labelled as penicillin-allergic in Northwestern Ontario was 3.1%. Oral amoxicillin challenge without prior skin testing proved to be a safe and effective approach for de-labelling low-risk children. Broader implementation of this strategy could enhance antibiotic stewardship, reduce healthcare-related costs, and improve patient care.