Why 97 per cent of people with a penicillin allergy may actually tolerate the drug

More than 97 per cent of people diagnosed as allergic to penicillin may not actually be, according to Australian doctors.

Melbourne researchers have found an allergy to the common antibiotic is in many cases misdiagnosed, which means more patients can be treated with it.

This is because many people are diagnosed in childhood but grow out of reactions, similar to food intolerances.

"We know it's very safe, we have almost 100 years' experience with the drug and it's really effective," Professor Jason Trubiano from Austin Health said.

"The vast majority were never allergic in the first place."

Researchers from the Austin Hospital re-tested 1000 patients with low-risk penicillin allergies, finding that 97 per cent who thought they were allergic were not.

Professor Trubiano said because penicillin can be tolerated by a wider demographic of people without harmful side effects, the news that many have been misdiagnosed is actually positive.

"It really gives patients the best chance of a cure," Professor Trubiano said.

Anybody who has been given a diagnosis of being allergic to penicillin can be re-tested at Austin Hospital on the spot.