About one in ten people report having a penicillin allergy. It’s the most common type of medication allergy, but experts are now finding many people think they have it when they really don’t.

Sarah Petro has lived the last 10 years believing she has an allergy to the antibiotic penicillin. The last time she took the drug, she had a severe reaction.

“I broke out in hives and had to go to the emergency room,” Petro said.

She’s been extremely careful to avoid penicillin ever since.

“It does make you think twice whenever you’re reaching for a medication,” said Petro.

But recently, Petro took a skin allergy test that revealed she’s not allergic to the medicine anymore.

“Most people with penicillin allergy are needlessly avoiding penicillin and penicillin-type drugs,” Dr. David Lang, an allergy and clinical immunologist, said.

Lang said about 90 percent of patients with a penicillin allergy will lose their allergy over time and be able to take the medicine without any risk.

“It’s important, because if you self-report penicillin allergy, this may be a barrier to you receiving optimal care,” said Lang.

Lang said it’s important to identify who can take penicillin, because in some cases, the medicine may be less costly, more effective, and pose fewer side effects than alternatives. The use of non-penicillin antibiotics could also lead to antibiotic resistance. You can find out if you still have the allergy with a simple skin test like Petro did.

“It was a great outcome,” said Petro.

Now Petro can say goodbye to her fear of an allergic reaction and hello to penicillin if she needs it.

The allergy testing has been around for decades and is completely safe. It’s what doctors use as a standard test for allergies. Lang said it’s critical to receive the test before making any changes, because you could have a severe reaction if you’re part of the 10 percent of patients that are still allergic to the drug.