Do You Really Have a Penicillin Allergy?

Using broad-spectrum antibiotics also leads to more drug-resistant bacteria — superbugs, like MRSA — which leave everyone more vulnerable. “If we can stop the use of these broad-spectrum drugs that kill everything, we won’t see as much C. difficile and resistant bacteria,” says Michael Blaiss, M.D., executive medical director at the American College of Allergy, Asthma and Immunology.

So why is it that, as a recent study showed, 90 percent of patients who think they have a penicillin allergy can actually tolerate the drug? “In the ‘50s, ‘60s and ‘70s, [penicillin] was used like candy,” says Bruce Gordon, M.D., a Massachusetts otolaryngologist. “A lot of kids had viral infections and developed rashes while taking penicillin. But it was because of the virus, not the penicillin. Still, nobody wanted to risk it because of the few people who have true and severe allergic reactions.”

Allergists say that both patients and doctors have been frequently confused by what a true allergic reaction to penicillin looks like. It's not, for instance, vomiting. Actual reactions include itchy hives, a swelling of the face and other areas, wheezing or difficulty breathing, and they occur within a few hours of taking the drug. “The timing is important; this happens within a few hours, not like hives that appear two weeks later,” Blaiss explains. “A lot of doctors say, ‘You might be allergic to penicillin. Just avoid it.’ ”

Many of those who were told as a child they had a reaction have spent decades avoiding penicillin. Yet after 10 years, most people outgrow the allergy, especially if it's a more typical and less severe one, Gordon notes. 

Naturally, if you’ve thought you are allergic to the antibiotic and avoided it your whole life, you still might not want to take a chance on a penicillin prescription. One solution is to see an allergist for a simple skin test. (You can’t get the test while on some medications, including beta blockers or antihistamines; check with your doctor about suspending them for the test, Blaiss says.) 

While at the allergist's office, you're watched for hives or swelling after a skin prick. If nothing happens, you might be given an oral dose of penicillin and kept in the office for about an hour to be sure you don’t have a reaction. Most patients don’t. “I’ve seen one person in 35 years develop some wheezing and hives after the test,” Blaiss says. “It’s done in an office, and any allergist is equipped to handle an anaphylactic reaction.”

A discussion with your doctor might reveal that such a test isn't even necessary. “If a history says a week later they had vomiting, I’ll just say, ‘Next time you can take penicillin,’ ” Blaiss says.