Most Penicillin Allergies Are Mistakenly Identified

A vast majority of people falsely believe they are allergic to penicillin when they are actually not, according to a new study.

Researchers at the Mayo Clinic (Jacksonville, FL, USA) conducted a study involving 384 patients attending a preoperative clinic between August 2012 and August 2013 who claimed they had a penicillin allergy. All were given a skin test, accepted as the gold standard to determining allergic susceptibility; the results showed that 94% tested negative for penicillin allergy. The researchers proposed that the reason most of the participants wrongly claim to be allergic is because they might have experienced an unfavorable response to penicillin in the past.

The researchers suggest that response such as hives, swelling, difficulties in breathing, anaphylaxis, or other minor reactions to penicillin lead many physicians to believe that they are allergic, despite never being clinically established. Even more common is the likelihood that patients did indeed have a clinically established allergic reaction to penicillin but, over time, that allergy went away, which is not atypical. The study was presented at the American College of Allergy, Asthma and Immunology (ACAAI) scientific meeting, held during November 2014 in Atlanta (GA, USA).

“A large number of people in our study who had a history of penicillin allergy were actually not allergic,” said lead study author allergist Thanai Pongdee, MD. “They may have had an unfavorable 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. With that in mind, their doctors prescribed different medications prior to surgery.”

“These results have a significant bearing on physicians’ prescriptions of antibiotics in a presurgical setting to ward off infection,” added Dr. Pongdee. “When patients tell their healthcare provider they are allergic to penicillin, the physician must substitute another antibiotic. These treatment alternatives may be more toxic, more expensive, and less effective than penicillin or antibiotics related to penicillin, such as cephalosporins.”

According to the researchers, the three antibiotics often used as substitutes, vancomycin, levofloxacin, and clindamycin, may actually have higher rates of adverse effects than penicillin or cephalosporins.

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