Austin Health research suggests millions of Australians may have been unnecessarily avoiding penicillin

A Melbourne-led study has revealed surprising results about whether people are really allergic to the drug.

Just one in 20 Australians in a clinical trial who thought they had an allergy to penicillin actually did, a world-first Melbourne-led study has revealed.

The randomised clinical trial also found more than 95 per cent of adults who have had a penicillin allergy were negative on testing.

The results mean, says senior author Jason Trubiano from Austin Health, that more than two million Australians may have been unnecessarily avoiding the best antibiotic available.

He says the driver of the research has been superbugs, but also ensuring people are given the right antibiotics to treat infections.

“Penicillin has been around for more than 75 years and is still the best,” Professor Trubiano said.

Austin Health professor Jason Trubiano says more than two million Australians may have been unnecessarily avoiding the best antibiotic available.

He said patients who have a penicillin allergy receive second-line antibiotics to treat common infections and this can result in treatment failures, superbugs and poor patient outcomes.

“This can be avoided as more that 95 per cent of patients that report a low risk penicillin allergy are negative on testing, meaning they are no longer allergic or were never allergic in the first place,” Professor Trubiano said.

“You can outgrow an allergy.”

Published overnight in JAMA Internal Medicine, the study was a collaboration between the Centre for Antibiotic Allergy and Research in the Department of Infectious Diseases at Austin Health in Melbourne and specialist allergy centres in North America.

It was called the Penicillin Allergy Clinical Decision Rule (PALACE) study and involved almost 400 adults, including 200 from Victoria.

Professor Trubiano says penicillin allergy is a major public health issue.

“These results are important for those adults who may have been told they were allergic to penicillin as children or people who had a reaction to it, but have since outgrown the allergy,” he said.

A 1943 image of Sir Alexander Fleming, the bacteriologist who discovered penicillin.

“Either way there is a group who have a low risk allergy, and that is in excess of two million Australians,” Professor Trubiano said.

He suggests adults who have a penicillin allergy ask to be retested under medical supervision or in a supportive health care setting such as a specialist clinic at a hospital.

The researchers reported it was crucial to address penicillin allergy and to accurately identify it as it can have significant implications for patient care.

The PALACE study is the first international study to evaluate a new approach to identify low-risk patients to determine the best way to test and treat them.

The researchers compared using a simple oral test with the existing skin scratch test that is more complicated, time-consuming and painful.

They used a specialised risk assessment tool called PEN-FAST on adults who were randomly assigned to receive either a direct oral penicillin challenge or the standard approach.

Professor Trubiano said the oral test proved as effective as the standard method and importantly, there were no significant differences in adverse events

He says it has paved the way for widespread use of the direct oral penicillin challenge as a safe and effective alternative to traditional skin testing.