About two million Australians think they are allergic to penicillin but the true number is closer to just 1 per cent of the population.

Until recently, patients had to have skin scratch tests to see if they would have a bad reaction to the medication but a simpler and cheaper test involving taking a small test dose has been shown to be just as effective.

Penicillin is considered a first-preference medication but people who are allergic must instead have second-line antibiotics, which aren’t as effective and can even fuel superbugs.

Some 382 patients who thought they were allergic took part in a study at Melbourne’s Austin Hospital. Just two of them had a reaction.

There was no difference in results for those who had the traditional scratch test compared to people who swallowed low doses of the medication, which is less expensive and more widely available.

The hospital’s director of infectious diseases Professor Jason Trubiano said about eight in 10 patients who were told they had the allergy grew out of it within a decade.

“What we found was really amazing in that giving a simple test dose is just as safe as doing scratch skin testing,” Professor Trubiano said.

“It means that more patients can have easy ways to test their penicillin allergies in the future and hopefully by doing that give back penicillin to these patients.

“They can use it for infections they have in the future and prevent a generation of superbugs.”

David Petrou grew up thinking he was allergic to penicillin so couldn’t take the medication when he was diagnosed with a stomach condition.

He was given other medication instead. It led to bad side effects and a secondary bacterial infection, so he was relieved to find out he was not actually allergic after taking part in the Austin study.

“It just relaxes me knowing that [taking it] is an option, that I’m going to have the best possible treatment,” Mr Petrou said.

“Don’t wait until you’ve got an issue like I did. I’d get tested now while you’re fine because it might just take out hassle down the track.”

People concerned they may have been misdiagnosed with a penicillin allergy should speak to their doctor. Testing is available at allergy or immunology clinics.

– AAP