Doctors urge patients to investigate penicillin allergies as study shows 90 percent can use it safely

Research from the Royal Perth Hospital (RPH) found that 90 per cent of people who believe they are allergic to penicillin are not, meaning they are missing out on highly effective treatment for infections.

Claire Italiano, chief of RPH’s infectious disease division, said 10 to 20 percent of patients admitted to the hospital reported being allergic to penicillin, but of that cohort, about 90 percent did not have the allergy.

In the past, a patient-reported allergy meant that doctors “generally err on the side of caution and [penicillin] antibiotics,” Dr. Italiano told Nadia Mitsopoulos on ABC Radio Perth.

“But we now know that avoidance of penicillin antibiotics often leads to worse outcomes for patients,” she said.

“What we’re finding is that sometimes people get an inferior antibiotic because we’re avoiding what they’re allergic to.”

How allergy errors arise

The reasons people come to believe they are allergic to penicillin are multiple and often related to a childhood incident, experts say.

Maryam Sherkat Masoum, an antimicrobial stewardship pharmacist at RPH, said people sometimes mistake a symptom of an illness for an allergic reaction.

“Sometimes people are given penicillin antibiotics for viral infections, and viral infections, especially in childhood, can cause rashes,” said Ms Sherkat Masoum.

“Sometimes the penicillin can be wrongly blamed for this.”

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Do you think you are allergic to penicillin? Maybe you aren’t – and here’s why

The other common reason she saw was that people mistook a penicillin side effect for an allergic reaction.

“Antibiotics, including penicillins, can have side effects such as feeling sick, feeling like you are going to vomit, vomiting or diarrhoea, headache or thrush,” said Ms Sherkat Masoum.

“These are all common side effects, but they are not allergies.

“Very often we can help you manage the side effects and actually complete your course of antibiotics and also not report it as an allergy.”

Ms Sherkat Masoum says people can grow out of a previous allergy.

“We now know that penicillin allergies are not lifelong,” she said.

“As with food allergies, you can grow out of your penicillin allergy.

“The numbers are quite impressive — after about 10 years, 80 percent of people with a penicillin allergy no longer have them.”

Why continue with penicillin?

Dr. Italiano said that until recently the prevailing belief was that if a patient reported being allergic to penicillin, it should be avoided at all costs to avoid a potentially life-threatening reaction, and that alternative antibiotics were prescribed.

“We considered risking an allergy to be one of the worst things we could do,” she said.

“But we know that’s actually not the case anymore.”

The front of the Royal Perth Hospital showing an ambulance bay and flagpoles.
Doctors say 90 per cent of patients at Royal Perth Hospital who report a penicillin allergy are not allergic.(ABC News: Glyn Jones)

Dr. Italiano said that when a person was diagnosed with an infection, the most desirable treatment option was to use a highly targeted antibiotic rather than a broad-spectrum drug that didn’t contain penicillin.

But she said it was less likely to be effective.

“It’s really only a last resort, or when people are very sick and we’re not sure what’s going on, that we use broad antibiotics,” said Dr Italiano.

“But sometimes we’re kind of stuck when people report a penicillin allergy because we can’t use that narrow one, that targeted one.”

She said the wider use of broad-spectrum antibiotics also had implications for antibiotic resistance and the potential to create superbugs.

“We have a number of antibiotics that are very broad,” said Dr. Italiano.

“They treat a lot of bacteria, and that might sound great, but it also means it disrupts individual gut flora and potentially contributes to antibiotic resistance.”

A close-up of three glass vials with penicillin stamped on them.
Penicillin is credited with saving millions of lives since its discovery.(Supplied: Sue Stafford)

Doctors examine allergies

If a patient with RPH now says they are allergic to penicillin, doctors try to investigate further whether they can safely receive the drug.

“Our first step is to take a further history from them, try to get more details on what antibiotic it was [they reacted to], what happened. Sometimes we go back to medical records,” Dr. Italiano said.

“I had a patient in their 90s who reported a penicillin allergy as a baby. I did the math. There was no penicillin back then, so we knew they weren’t allergic.

“Sometimes we can [allergic] label at that time.”

Dr. Italiano says doctors do a risk assessment after taking a medical history.

“If the chance of someone having an allergy is very low, we can challenge them,” she said.

“The first step would be with a small dose of an oral penicillin antibiotic. If people don’t have a problem with that, we’ll try to de-label them and put them on the most appropriate antibiotic.

“And for the more complicated cases, where people do have an allergy, we will involve our immunology colleagues.”

Dr. Italiano says that if people have been told they have a penicillin allergy, they should continue to tell their doctor, but ask their GP to look at their medical history and investigate whether it is safe for them to take penicillin.

Doctors urge patients to investigate penicillin allergies as study shows 90 percent can use it safely

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