Doctor Maria Duggan found out when she was a baby.
"My whole life I've had this label," said Duggan.
Lakisha Edmonson had a reaction to penicillin when she was 8-years-old.
"They were like, 'don't ever give this to her again. She's allergic to it," said Edmonson.
25 to 30 million Americans believe they're allergic to the life saving antibiotic penicillin, but according to doctors at Vanderbilt, 96% of them actually are not.
"The label gets put in their chart for something that happened when they were a kid and those events, it turns out, are not always penicillin allergy," said Doctor Cosby Stone Jr, an allergist at Vanderbilt University Medical Center.
Stone said people who can't take penicillin are more likely to have infections after surgery.
They're more likely to die from infections and more likely to die during cancer treatments.
So the more fake allergies they can rule out, the better.
"Not only is it going to save your life, it's also going to improve the quality of healthcare that you're going to receive," said Stone.
The first test involves a skin prick.
Next they put a small amount under your skin.
If both tests are negative, you take a dose by mouth.
"The whole thing takes 15 minutes, plus 15 minutes, plus an hour of observation so about 2 hours at the most," said Stone.
Stone said anyone who thinks they're allergic should do it.
People like Duggan, who now knows, she can take penicillin whenever she needs it.
"Getting the testing and knowing, for sure, that I was no longer allergic was very reassuring," said Duggan.
You can have the test performed at Vanderbilt's ASAP clinic located at 2611 West End Ave Suite #210. To make an appointment call (615) 936-2727.