Is penicillin-allergy rate overstated?

The number of people allergic to penicillin may be much smaller than physicians currently suspect, new data suggest.

During 3 months last year, researchers identified 24 people in the intensive care unit of the Cleveland Clinic whose medical charts showed a history of penicillin allergy. But when the researchers subjected 21 of these patients to skin-scratch tests for penicillin reactions, the results were negative for all but one.

Either these patients had misreported the drug allergy, or it had worn off over the years. Three patients weren't tested because, according to their medical history, they had once responded to the antibiotic with a life-threatening allergic reaction, in which a person's throat can swell shut. A scratch test could have triggered such a reaction, says study coauthor Alejandro C. Arroliga, a critical-care physician at the clinic.

Half of the 20 people who showed no allergy in the test received the antibiotic or a related drug as part of their treatment. None had an adverse reaction, Arroliga and his team report in the October CHEST. Preliminary data on a larger group of patients appear to confirm the initial study, suggesting that people reporting the allergy should be tested, Arroliga says.

Arroliga and his colleagues estimate that 10 to 20 percent of people in the United States report a penicillin allergy. Indeed, a recent study by Collin E. Lee and her colleagues at Northwestern Memorial Hospital in Chicago shows that 16 percent of patients claimed to be allergic to penicillin.

Such a note on a person's medical chart can lead physicians to prescribe alternative antibiotics that may not be best suited for the patient's ailment, assert the Chicago researchers. That puts patients who actually aren't allergic to penicillin at an unnecessary risk of an infection persisting, they argue. It also leads to an overuse of alternative drugs and may enable bacteria to become resistant to those newer medications, the scientists warn in the October ARCHIVES OF INTERNAL MEDICINE.