Second-guess that allergy to penicillin
Millions of Americans who believe they are allergic to penicillin are not actually allergic. But they are steered away from using some of the safest, most effective antibiotics, relying instead on substitutes that are often pricier, less effective and more likely to cause complications such as antibiotic-resistant infections.
Those are the conclusions of a new paper on penicillin allergy. Experts in allergy and infectious disease, including the paper’s authors, are now urging patients to ask doctors to review their medical history, and reevaluate whether they have a true penicillin allergy.
The evaluation, which may require allergy skin testing and ideally should be done while people are healthy, is especially important for pregnant women, people with cancer and those in long-term care, and anyone anticipating surgery or being treated for a sexually transmitted infection.
“When you have a true infection that needs to be treated, the physician will see you have the allergy and not question it,” said Dr. Erica S. Shenoy, lead author of the new report, published last month in JAMA. “What we are trying to do is get people to question it.”
Though an allergy can develop at any age, penicillin allergies are often first recorded in childhood, when penicillin is the No. 1 antibiotic prescribed. If a child on penicillin develops a rash or other symptom and it is erroneously attributed to the drug, the allergy label sticks. “From then on it’s on the chart,” said Shenoy, associate chief of infection control at Massachusetts General Hospital.
The review was carried out with input from the boards of three professional medical organizations: the American Academy of Allergy, Asthma and Immunology; the Infectious Diseases Society of America; and the Society for Healthcare Epidemiology of America. All three groups endorsed the findings.
There is no question some people have potentially life-threatening allergic reactions to penicillin, but the label appears to have been applied far too broadly, experts say. About 10 percent of Americans report having a penicillin allergy, and the rate is even higher among older people and hospital patients, 15 percent of whom have a documented penicillin allergy.
But studies that have gone back and conducted allergy skin testing on patients whose records list a penicillin allergy have found the overwhelming majority test negative. A 2017 review of two dozen studies of hospitalized patients found that overall, 95 percent tested negative for penicillin-specific immunoglobulin E, or IgE, antibodies, a sign of true allergy.
“We used to say 9 out of 10 people who report a penicillin allergy are skin-test negative,” said Dr. David Lang, president-elect of the American Academy of Allergy, Asthma and Immunology and chairman of allergy and immunology in the respiratory institute at the Cleveland Clinic. “Now it looks more like 19 out of 20.”
Patients can get mislabeled as allergic to penicillin in a number of ways. They may experience bad drug reactions like headaches, nausea or diarrhea, which are not true allergic reactions but are misinterpreted. Alternatively, they may develop a symptom like a rash, which is indicative of a real allergic reaction but could be caused by an underlying illness and not by the drug.
And many people who have avoided penicillin for a decade or more after a true, severe allergic reaction will not experience that reaction again. “Even for those with true allergy, it can wane,” said Dr. Kimberly Blumenthal, the review’s senior author, who is an allergist and an assistant professor at Harvard Medical School. “We don’t really understand this, but once you’ve proven you’re tolerant, you go back to having the same risk as someone who never had an allergy” to penicillin.
Don’t challenge yourself to penicillin on your own, experts warn. Patients who have been told they’re allergic to penicillin should talk to their doctors, who should take a careful history and review the symptoms of the reaction.