Updated 10 November 2014

Think you're allergic to penicillin? Maybe not

In studies, the vast majority of people who said they had a penicillin allergy showed no evidence in skin tests.


Many Americans may check the box "allergic to penicillin" on medical forms, but new research suggests that most of them are mistaken.

Follow-up testing revealed that most people who believed they were allergic to penicillin were actually not allergic to the antibiotic, according to two new studies.

In one study, 94 percent of 384 people who believed they were allergic to penicillin tested negative for penicillin allergy.

And in the second study, penicillin skin testing was performed on 38 people who believed they were allergic to the antibiotic, and all of them tested negative for such an allergy.

The studies were to be presented Friday at the annual meeting of American College of Allergy, Asthma and Immunology (ACAAI), in Atlanta.

"A large number of people in our study who had a history of penicillin allergy were actually not allergic," Dr. Thanai Pongdee, lead author of the first study, said in an ACAAI news release.

"They may have had an unfavourable response to penicillin at some point in the past, such as hives or swelling, but they did not demonstrate any evidence of penicillin allergy at the current time," Pongdee explained.

Read: Be allergy alert

Misconceptions may affect treatment

But such misconceptions might affect treatment. Once told that the patient thought he or she was allergic to penicillin, "their doctors prescribed different medications prior to surgery," Pongdee said.

Those alternative antibiotics that may be more toxic and/or expensive, the ACAAI noted.

Two experts said the studies bring up an important point.

"An evaluation by an allergist for the penicillin and other beta lactam antibiotic allergy is important, is cost-effective and will decrease the use of other more expensive medications," said Dr. Luz Fonacier, head of the allergy section in the division of rheumatology, allergy and immunology at Winthrop-University Hospital in Mineola, N.Y.

"Penicillin skin testing is the most reliable method for evaluating immediate hypersensitivity reaction to penicillin," she said. "When negative -- which is most of the time -- the patient can then most likely tolerate penicillin."

Dr. Punita Ponda is assistant chief of the division of allergy and immunology at Cohen Children's Hospital of New York, in New Hyde Park, N.Y.

She agreed that "there is often an over-representation of penicillin allergy historically, which can lead to avoidance of this very useful group of antibiotics."

According to Ponda, "This particularly impacts clinical care when surgical interventions are planned where the use of antibiotics is very likely during the surgical procedure, or during the pre- or post-surgical periods."

Experts note that findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.

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