Females are nearly five times more likely than males to have skin test results that show they’re allergic to penicillin, according to findings reported here Sunday at the annual meeting of the American College of Allergy, Asthma, and Immunology.

“The finding of a gender disparity for penicillin allergy is relatively new,” Dr. James T. Li, from the Mayo Clinic in Rochester, Minnesota, told AMN Health.

“Previous reports have shown trends suggesting an increased risk for women,” he explained, but in those studies the results could have occurred by chance. “Our study is the first, to my knowledge, to have enough subjects to achieve statistical significance.”

Li’s team studied 1759 people who reported a history of penicillin allergy and participated in a skin-testing trial designed to reduce the use of broad-spectrum antibiotics during surgery. If the skin test showed no allergy, a penicillin-type drug was given in the operating room.

“Previous studies have shown that only about 10 percent of people who say they have a penicillin allergy, actually do when skin tested,” Li commented. Also, “it’s been shown that it is very safe to give penicillin-related drugs to patients with an apparent history of penicillin allergy but a negative skin test.”

The researchers found that the strategy did, in fact, reduce the use of broad-spectrum antibiotics and help prevent germs developing resistance to drugs.

The data also produced an unexpected finding: penicillin allergy was much more common in female than in male patients.

Overall, 64 patients had a positive skin test to penicillin - just 11 were male, while 53 were female.

Li said the reasons why women might be predisposed to penicillin allergy are unclear. However, if other types of allergy reflect what occurs with penicillin allergy, “estrogen and other hormones don’t seem to play a major role,” he noted.