18 July 2023

One in 10 people that present to hospital have been diagnosed with a penicillin allergy. However, less than 10 per cent of those patients are truly allergic.

This happens because while it is not uncommon for a child to have a penicillin allergy, in many cases, their allergy will fade in time as they become older. The difficulty is that to test for a penicillin allergy is a skin test that is rather time-consuming and can be painful.

David was 36 years old when he was diagnosed with Helicobacter pylori in 2021 – a bacterial infection of the stomach. However, due to a documented penicillin allergy from childhood, he couldn't take the prescribed medication, Amoxicillin, and underwent a substitute therapy.

“I was two years old when I had an adverse reaction to penicillin and was diagnosed with having an allergy. It hasn’t really been an issue for me, that is until recently when I was diagnosed with h’plyori (Helicobacter pylori),” says David.

The second-line antibiotics resulted in David developing Clostridioides difficile (known as C. Diff) - a bacteria that causes painful inflammation in the colon and can be fatal.

“It was awful, the triple antibiotics I took to treat my h-plyori were horrendous. It didn’t eradicate my h-ployir, and I had about 15 side effects for months after the treatment. And to make matters worse – I got C.Diff on top of it.”

Shortly after, David learned of the PALACE study at Austin Health - a world-first randomised control trial undertaken by a team of researchers from specialised centers in North America and Australia – including senior author Professor Jason Trubiano from the Centre for Antibiotic Allergy and Research, Department of Infectious Diseases.

The study enrolled 382 adults, including David, who were assessed using a specialised risk assessment tool called PEN-FAST. Participants were randomly assigned to receive either a direct oral penicillin challenge or the standard approach, which involves penicillin skin testing followed by an oral challenge. The primary goal was to determine if the direct oral penicillin challenge was as effective as the standard method.

David was 36 years old when he was diagnosed with Helicobacter pylori.

The study found that only one patient (0.5 per cent) in each group experienced a positive reaction to the penicillin challenge. This demonstrates that the direct oral penicillin challenge is just as effective as the standard method.

Following his participation in the PALACE study, David was confirmed to have no penicillin allergy. With this new information, David consulted his gastroenterologist once again and successfully took Amoxicillin with no allergic response.

“After the PALACE Study, it’s allowed me to have a much smoother treatment to eradicate the h’plyori. It’s great being able to move forward knowing I can have penicillin as an option which gives me a lot of comfort. You never know when you're going to need it. I wish I had had my allergy tested earlier.

I’d been told regularly by GP’s that it was worth getting my allergy tested as it’s very common for people to have adverse reactions to penicillin when they are young but that doesn’t mean they are allergic. But I never made the time to get tested.”

The findings of the PALACE study have wide-ranging implications, particularly for the more than two million Australians who will have access to the simplified penicillin allergy testing procedure. By accurately identifying low-risk penicillin allergy patients, healthcare providers can ensure appropriate antibiotic prescriptions,

The PALACE study represents a major advancement in addressing the global issue of penicillin allergies and paves the way for the widespread adoption of the direct oral penicillin challenge as a safe and effective alternative to traditional skin testing.