Nineteen out of 20 people diagnosed as allergic to penicillin may not actually be allergic at all, leading to longer hospital stays and antibiotic resistant infections, according to Erica Shenoy, MD, PhD, associate professor at Harvard Medical School and associate chief of infection control at Massachusetts General in Boston, who is a coauthor of a new review, published on January 15, 2019, in the Journal of the American Medical Association (JAMA), focusing on the management of penicillin allergy. The boards of three professional medical organizations contributed and endorsed the review and its findings: the American Academy of Allergy, Asthma, & Immunology, the Infectious Diseases Society of America, and the Society of Healthcare Epidemiology of America.
Serious Consequences of Being Wrongly Labeled ‘Penicillin-Allergic’
According to the American College of Allergy, Asthma, & Immunology, up to 10 percent of people report being allergic to penicillin, making it the most commonly reported drug allergy. But recent scrutiny of reported penicillin allergies has revealed widespread misdiagnosis. A review published in March 2017 in the European Journal of Allergy and Clinical Immunology looked at 24 studies of hospitalized people and found that 95 percent of those who reported being allergic to penicillin actually tested negative for penicillin-specific immunoglobulin E, or IgE, antibodies, the indicator of a true allergy. When you have a reported penicillin allergy, it not only decreases the likelihood that you will be prescribed a penicillin when indicated, but very often it will decrease the chance that you will be prescribed other beta-lactam drugs, like cephalosporins, according to Dr. Shenoy. All penicillins are beta-lactam antibiotics, and they are considered among the safest and most efficacious treatments for many infections. For many common syndromes and specific infections, beta-lactams are the treatment of choice, and using non-beta-lactams is associated with poor outcomes, according to Shenoy. “For example, beta-lactams are first choice antibiotics used to prevent infections from surgery. Using an alternative antibiotic because of a reported penicillin allergy has been associated with increased risk of post-operative infection," says Shenoy. This happens because the penicillin substitutes are less capable of killing the bacteria or are broader spectrum and therefore not as precisely aimed at the particular bacterium that need to be targeted, says N. Franklin Adkinson, MD, professor of medicine in allergy and immunology at Johns Hopkins Medicine in Baltimore. “These drugs tend to promote either the persistence of these organisms or the development of resistance,” says Dr. Adkinson. In a recent UK study, published in June 2018 in BMJ, patients who had been flagged in their chart as allergic to penicillin had almost a 70 percent greater risk of methicillin-resistant Staphylococcus aureus (MRSA) and about a 26 percent greater risk of Clostridium difficile (C. diff) than people the same age and sex who were not labeled as allergic to the drug.
Higher Costs Come Along With Misdiagnosis of Penicillin Allergy
A false diagnosis of a penicillin allergy means an additional financial burden to both individuals and the overall healthcare system. People who are labeled as allergic to penicillin will typically stay in the hospital longer, take longer to get rid of the infection because of the alternative antibiotics they’ve been given and more likely to develop a resistant organism (such as MRSA), says Adkinson.
Why Are So Many People Wrong About Their Penicillin Allergy?
There can be a variety of reasons why a person might think they’re allergic to penicillin, according to Kimberly Blumenthal, MD, an allergist at Massachusetts General Hospital and assistant professor at Harvard Medical School in Boston, who is also a coauthor of the JAMA report. “Many reported penicillin allergies are diagnosed in childhood, and when a penicillin antibiotic is prescribed to children with an infection, a rash from the virus may be misattributed to the antibiotic,” says Dr. Blumenthal. From that point on, the penicillin allergy is on the patient’s chart, potentially never to be questioned again, she says. This measles-like rash is fairly common, according to Adkinson. “About 3 to 10 percent of courses of penicillin result in that kind of rash. It’s technically an allergy, but it’s benign in the sense that it takes care of itself if you stop the drug or it’s easily treated with a few days of steroids if you wanted to continue the drug,” he says. Many reactions listed as “allergies” are not really allergies and actually could be side effects, intolerances, or even patient preference, according to Blumenthal. “It is important to recognize that most side effects and intolerances are not contraindications to receiving the medication again,” she says. Even true penicillin allergy can fade over time, says Blumenthal. “It is highly likely that a patient who had a true penicillin allergy — like hives, swelling, or anaphylaxis — could tolerate penicillin after time elapses,” she says.
What Should You Do if You’ve Been Told You’re Allergic to Penicillin?
“I would encourage all patients, including parents accompanying their children to pediatrics visits, to discuss any reported allergies, and specifically penicillin allergies, with their doctor,” says Theresa Rowe, DO, assistant professor of general internal medicine and geriatrics at the Northwestern Feinberg School of Medicine in Chicago, and a coauthor of the review. “As a patient, you can provide the important information to help the clinicians understand better if this was a true penicillin allergy,” she adds. Once you review your allergy history, your doctor might recommend a planned course of action that may include penicillin allergy testing, as described in another article published on January 15, 2019, in the Journal of the American Medical Association. This includes a skin prick test and an intradermal test, where a small needle is inserted under the skin. If those tests are negative, an oral dose of penicillin is administered under doctor supervision as the final test of the allergy.
