Most Australians Who Report Penicillin Allergy Are Not Allergic, New Guidelines Say

Penicillin was thought to cause allergies in about 10% of Australians, or 2.8 million people, but the latest evidence shows up to 90% of those reporting an allergy do not have one. The updated guidelines, published in the Journal of Allergy and Clinical Immunology, provide the first peer-reviewed advice for GPs and other health professionals on diagnosing and managing the allergy, and when to refer to a specialist.

Prof Michaela Lucas, a clinical immunologist at the University of Western Australia, said misdiagnosis occurs for various reasons: people may experience a rash or nausea after taking penicillin and assume it is an allergy, or doctors may record side-effects as allergies to be cautious. Others were told by a parent they had a reaction as a child and carry the diagnosis into adulthood without questioning it, she said, while some side-effects may be due to the illness itself rather than the medicine.

Lucas said penicillin is an important narrow-spectrum antibiotic that targets the specific bug causing an infection. “Once you have to avoid narrow classes of drugs, you have to use broader spectrum antibiotics which have a bigger impact on your gut microbiome … and allow superbugs to come in and take residency,” she said. She added that antimicrobial resistance matters beyond the individual patient because resistant bacteria can spread between people and through communities.

Dr Nick Cooling, chair of the Royal Australian College of General Practitioners’ allergy special interest group, said the guidelines were based on the latest evidence and a consensus report from a range of medical specialties. He hopes the guidance will cut health costs and ease the burden on immunologists. “We know that people who have a penicillin allergy label go to hospital more. They spend longer in hospital, and they also cost the system more,” he said, citing more treatments needing to be trialled, side-effects, and delays in finding alternatives.

Cooling urged patients to raise the question of a penicillin allergy with their GP, and said that where the potential risk of harm is low, doctors could give penicillin and monitor for symptoms. But he warned: “No one should try taking penicillin themselves to find out whether they are allergic. Antibiotics should only be taken when prescribed for the individual taking them.”

Tammy Prescino, whose 70-year-old mother and 12-year-old daughter are both diagnosed with penicillin allergy, welcomed the changes. She worries her mother could miss out on the benefits of penicillin if she gets an infection, and plans to see a doctor to get her family reassessed.