Australian allergy body updates penicillin guidance as most people who report an allergy may not have one

The Australasian Society of Clinical Immunology and Allergy (ASCIA) has changed its guidance on penicillin allergy, and The Guardian reported on 21 October 2026 that most Australians who report the allergy are not truly allergic. According to the newspaper, the latest evidence it cited suggests that up to 90 per cent of people reporting a penicillin allergy do not have one.

Penicillin is an antibiotic, a medicine used to treat bacterial infections. Penicillin was previously thought to cause allergies in 10 per cent of Australians, or about 2.8 million people, according to The Guardian. Many of those people carry the label on their medical records, sometimes for life.

Prof Michaela Lucas, a clinical immunologist at the University of Western Australia, said that misdiagnosis can happen in three main ways. People may mistake a rash or nausea for an allergy, doctors may record side-effects as allergies, or childhood reports of a reaction may be carried into adulthood without being questioned.

The label has costs beyond the individual. Dr Nick Cooling, chair of the allergy special interest group of the RACGP, said people with a penicillin allergy label go to hospital more often, stay longer and cost the health system more. The guideline changes are aimed at reducing hospital stays and addressing antimicrobial resistance, the term for bacteria that are no longer stopped by the drugs meant to kill them.

ASCIA has published new guidelines titled Guidelines for the management of adult penicillin allergy in the Journal of Allergy and Clinical Immunology: Global. The guidance, which ASCIA posted on its website on 19 October 2026, is intended to help health professionals identify adult patients whose label may need reassessing. The Guardian described it as the first peer-reviewed and updated advice on diagnosing and managing penicillin allergy, and on when to refer a patient to a specialist.

A 2020 consensus statement said testing should be prioritised for groups including people who have frequent infections requiring antibiotics, and that removing an incorrect label reduces illness and death, antibiotic resistance and economic costs. ASCIA's patient information describes an antibiotic allergy challenge as a procedure in which doses of the suspected antibiotic are given under supervision.

ASCIA's clinical update also warns that fatal anaphylaxis, a severe allergic reaction affecting the whole body, can occur if penicillin is given to a highly allergic patient.