NEW YORK (CBSNewYork) — It’s not uncommon to hear of someone who has an allergy to penicillin, but many people who think they’re allergic may not be allergic at all.

So what’s the harm if you avoid penicillin even if you’re not allergic?

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As CBS2’s Dr. Max Gomez explained, using a different antibiotic could cause more side effects, not work as well, and will likely be more expensive.

Claire Branman is among the millions of Americans who think they have a penicillin allergy,

“I started saying since I was a little kid because my mom told me when I was a baby I had an allergic reaction,” she said.

At 26-years-old Claire is now getting an allergy test to find out for sure, and here’s why.

“Ten to fifteen percent of the population thinks that they are allergic to penicillin, but in actuality less than one percent are truly allergic to penicillin,” Dr. Aleena Banerji, Allergist, Mass General Hospital.

That’s right less than one percent.

“When we’re children and we have this added to our medical record, then over time as we get repeated infections we don’t ever address the issue again,” Dr. Kim Blumenthal, Allergist, Mass General Hospital said.

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For Claire the alternative antibiotic for a minor dental procedure led to much bigger health problems.

“It was a nightmare, and I actually ended up having my stomach kind of messed up for a few years since then, which I thought if I wasn’t allergic to penicillin I could have avoided that,” she said.

A penicillin allergy prevents patients from taking any of the penicillins including amoxicillin and augmentin.

Allergists at Mass General Hospital in Boston have developed an app to help doctors quickly identify patients who should get tested. It’s now being used at two Harvard affiliated hospitals.

“And then it helps the doctor or the nurse ask more detailed questions that are usually, sort of allergy specialist knowledge, but sort of at the palm of your hands,” Dr. Blumenthal said.

After two skin tests Claire found out she is not allergic to penicillin which could make a world of difference the next time she gets sick.

Anyone who believes they have a penicillin allergy should get tested, especially if they don’t recall why someone told them they were allergic. The test should be conducted when a person is health, not when they are sick and need an antibiotic.

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