04/08/2026
Most people who think they’re “allergic to penicillin” actually aren’t. And a new international study shows there’s a simple, safe way to find out.
Around 10% of people report a penicillin allergy, but more than 95% of them are mistaken. Many were labeled as children after a rash that was more likely from the infection than the antibiotic, and the label just never got questioned or reassessed. The problem: avoiding penicillin can lead to using less effective antibiotics with more side effects, a higher risk of antibiotic-resistant infections, and longer hospital stays.
In this new study of 5,121 hospitalized adults across 40 hospitals in 8 countries, clinicians used a smartphone app to sort patients into risk groups based on their allergy history. Those with a low-risk history (like a mild childhood rash rather than anaphylaxis) were offered a “direct oral challenge”- a single dose of penicillin given under observation.
Of 1,573 patients who underwent the challenge, 96% were safely cleared of the allergy label (meaning they no longer carried a penicillin allergy in their chart). Only 71 people reacted, and just 6 (0.4%) had serious reactions. None had anaphylaxis or needed ICU care. Most challenges were handled by non-allergists, such as pharmacists, nurses, and other clinicians, showing that this can work even where allergy specialists are scarce.
Clearing the allergy label significantly changed prescribing. Patients who had the challenge were 13 times more likely to get penicillin in the next 90 days and were significantly less likely to receive the replacement antibiotics that drive resistance. They also had a lower risk of multidrug-resistant infections.
For people with low-risk histories, direct oral challenge is an effective tool to safely clear inaccurate penicillin allergy labels, improve treatment, and help fight antibiotic resistance. Anyone who has carried a penicillin allergy label for years may want to ask their healthcare team whether formal reassessment makes sense.
