About one in 10 people who believe they are allergic to penicillin are not, according to new international research suggesting that most allergy labels recorded in hospitals are incorrect.
The study, led by the University of Melbourne and published in Clinical Infectious Diseases, found that 95 percent of patients who reported a penicillin allergy were able to safely take the antibiotic after testing.
Researchers analyzed data from more than 5,000 patients across 40 hospitals in Australia, the UK, the United States, Canada, Malaysia, South Africa, Hong Kong, and New Zealand as part of the iNAAN study (International Network of Antibiotic Allergy Nations). They used a method known as a direct oral challenge, in which patients were given a small dose of penicillin under medical supervision and monitored for reactions.
Why Are So Many People Misdiagnosed?
Of 1,573 patients who reported a penicillin allergy and underwent testing, about 95 percent (1,502 patients) were cleared and had their medical records corrected. The findings suggest that many allergy labels are the result of misdiagnosis in childhood, symptoms that were never properly investigated, or reactions that have faded over time.
“Most are not truly allergic, often because they were misdiagnosed in childhood, outgrew it, or it’s been years since their last reaction,” lead author Dr. Jason Trubiano, professor and head of infectious diseases at the University of Melbourne, said in a statement.
The findings represented a “game changer” for how penicillin allergies are managed, and could allow testing to be rolled out more widely in hospitals, he said.
“For the first time, we have shown this approach can be safely implemented at scale across entire hospital systems,” Trubiano said.
When penicillin cannot be used, doctors often prescribe alternative antibiotics that can be less effective and more likely to contribute to antimicrobial resistance. These alternatives have also been linked to longer hospital stays, higher costs, an increased likelihood of intensive care admission, and, in severe cases, can lead to a higher risk of death.
They can also contribute to the rise of methicillin-resistant Staphylococcus aureus and Clostridioides difficile, two bacterial infections that can become resistant to antibiotics, making infections more difficult to treat.
Removing inaccurate allergy labels allows patients to access first-line treatments.
“For patients, that means faster access to the most effective antibiotics and better treatment outcomes,” Trubiano said.
Dr. James Yun, chair of the Australasian Society of Clinical Immunology and Allergy’s drug allergy committee, said there are additional reasons for misdiagnoses.
“Children who develop a mild rash or itching while taking penicillin for an illness may be labeled as allergic, even though the rash could have been caused by the viral infection itself,” he told The Epoch Times. “In other cases, common side effects such as an upset stomach, diarrhea, or headache are mistaken for an allergic reaction.”
The study also found that the testing method could be safely carried out by non-specialists, such as pharmacists, which opens the door to conducting testing in regular hospital settings. Researchers say the approach could help reduce unnecessary use of broader-spectrum antibiotics and improve treatment outcomes for patients worldwide.
Improvements to Testing Methods
Traditional methods of testing for penicillin allergies have been difficult to scale, Yun said.
“Testing for penicillin allergy involved a detailed assessment by an allergy specialist, followed by blood tests and skin tests,” he said.
The process is time-consuming and resource-intensive, and constrained by the limited number of trained clinicians, effectively making it “practically impossible” to assess everyone, Yun said.
The direct oral challenge used in the study offers a simpler alternative. Low-risk patients can be assessed directly with a supervised oral dose of penicillin without extensive preliminary skin testing and specialist oversight. This streamlined approach reduces the need for specialized resources and allows testing to be delivered more efficiently—making it a more practical option for scaling penicillin allergy assessment in routine hospital care.
“This is an important step forward,” Yun said. “It means people who are unlikely to have a true penicillin allergy can be assessed and cleared more easily and safely, without needing to see an allergy specialist.”