Why Antibiotic Allergy Labels Deserve a Second Look

In modern medicine, antibiotics are among the most powerful tools for preventing and treating life-threatening bacterial infections. Their effectiveness, however, often depends on using the right drug at the right time.

Recognizing this challenge, Yale researchers sought to better understand the prevalence of antibiotic allergy labels among patients undergoing bone marrow transplantation, which patients are most likely to carry them, and how often those labels reflect true allergy. Their findings were recently published in the Journal of Allergy and Clinical Immunology: In Practice.

According to Ami Belmont, MD, assistant professor of medicine (rheumatology, allergy, and immunology) at Yale School of Medicine (YSM), many patients may unnecessarily carry allergy labels—entries in the medical record suggesting a patient should avoid a medication—to commonly used antibiotics, including penicillin, cephalosporin, and sulfonamide antibiotics. These labels may lead clinicians to rely on broader, less effective, or more toxic alternatives.

In many cases, Belmont says, the documented allergy does not reflect a true allergic reaction.

“Many antibiotic allergy labels are based on reactions that occurred years ago, often in childhood, and were never formally evaluated,” Belmont says. “For example, among patients who report a penicillin allergy, over 95% can typically tolerate penicillin. Antibiotic allergy labels may reflect a rash that developed for a reason other than allergy, such as a virus. In the case that someone was allergic to penicillin, it is often outgrown over time.”

In these situations, Belmont notes, the potential benefits of using a first-line antibiotic may outweigh potential risks, and evaluating and testing for allergy may be warranted.

For immunocompromised patients undergoing bone marrow transplantation, including many with leukemia, lymphoma, or other blood disorders, the consequences of suboptimal antibiotic selection are particularly significant. These patients experience profound immunosuppression and face a heightened risk of serious infection. Unnecessarily avoiding first-line antibiotics may lead to increased complications, longer hospital stays, and poorer clinical outcomes, says Belmont.

In the study, Belmont, her mentor E. Jennifer Edelman, MD, MHS, professor of medicine (general medicine) at YSM, and colleagues found that 18.5% of bone marrow transplant patients carried at least one antibiotic allergy label, most commonly to penicillin antibiotics. The likelihood of having a documented allergy varied by patient characteristics, and formal allergy testing was infrequently performed. When testing did occur, most labels were disproven, highlighting the gap between documented allergy and true immune-mediated hypersensitivity.

“Formal evaluation and allergy testing allow us to clarify whether a true allergy exists and, when it doesn’t, safely remove that label,” says Belmont.

Belmont hopes the findings will encourage clinicians to more carefully reassess antibiotic allergy labels, particularly in high-risk populations such as bone marrow transplant patients.

“Clarifying antibiotic allergy labels is a relatively low-risk intervention that can have meaningful downstream effects,” Belmont says. “For immunocompromised patients, being able to use first-line antibiotics can make a significant difference in both short- and long-term outcomes.”

Rheumatology, Allergy and Immunology, one of 10 sections in the Yale Department of Internal Medicine, is dedicated to providing care for patients with rheumatic, allergic, and immunologic disorders; educating future generations of thought leaders in the field; and researching fundamental questions of autoimmunity and immunology. To learn more, visit Rheumatology, Allergy, and Immunology.