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 re-evaluate 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 earlier this 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, she said. If a child on penicillin develops a rash or other symptom and it is erroneously attributed to the drug, the allergy label sticks, often for life.
“From then on it’s on the chart,” said Dr. 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 medical records list a penicillin allergy have found that the overwhelming majority test negative. A 2017 review of two dozen studies of hospitalized patients found that over all, 95 percent tested negative for penicillin-specific immunoglobulin E, or IgE, antibodies, a sign of true allergy.
“We used to say nine out of 10 people who report a penicillin allergy are skin-test negative. Now it looks more like 19 out of 20,” 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.
Patients can get mislabeled as allergic to penicillin in a number of different 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.
It’s a good idea to find out if your allergy is real or not because penicillin antibiotics, which are part of a group of drugs called beta-lactam antibiotics, are among the safest and most effective treatments for many infections. Beta-lactams are the treatment of choice for Group A Streptococcus, which can cause pneumonia, toxic shock and other syndromes; Group B Strep, which causes meningitis; Staphylococcus aureus and other pathogens. Beta-lactams are used prophylactically to prevent infections during surgery, and studies have found that patients with penicillin allergies who are given second-line antibiotics before surgery had a substantially greater risk of a surgical site infection. Beta-lactams are also the first line treatment for syphilis and gonorrhea.
Substitutes like fluoroquinolones, clindamycin, vancomycin and third-generation cephalosporins are available, but they are often both less effective and more expensive, and many are broader spectrum antibiotics, which can lead to the development of resistant organisms and other side effects, experts say. Studies have shown that patients with penicillin allergies are at increased risk for developing serious infections like Clostridium difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant enterococcus.
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.
If the past reaction to penicillin included symptoms like headache, nausea, vomiting and itching, or the diagnosis was made based on a family history of the allergy, the patient is considered low risk and may be able to take a first dose of penicillin or a related antibiotic, such as amoxicillin, under medical observation.
If the past reaction included hives, a rash, swelling or shortness of breath, patients should have penicillin skin testing, which involves a skin prick test using a small amount of penicillin reagent, followed by a second test that places the reagent under the skin if the first test is negative. If both tests are negative, the patient is unlikely to be allergic to penicillin, and an oral dose may be given under observation to confirm.