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Accurate labeling of penicillin allergies is essential, but unconfirmed penicillin allergies may have negative effects on individual and public health, according to experts.

A trend toward “de-labeling” by testing individuals with documented penicillin allergies is gaining steam, in part as a way to reduce antibiotic use and curb the emergence of more resistant bacteria, according to Upeka Samarakoon, PhD, of Massachusetts General Hospital, Boston, and colleagues in a review article published in 2023 in the Annals of Allergy, Asthma, and Immunology. The article outlined the benefits of de-labeling and identified how patients are labeled with a penicillin allergy.

Individuals acquire a penicillin allergy label either by reporting a past reaction to penicillin or displaying a reaction recorded by a healthcare provider. Removing the allergy label from a patient’s medical record may involve an evaluation of reaction history and often following an in-office drug challenge, according to the authors.

Why Lose the Label? 

Penicillin antibiotics are first-line treatments for infections commonly treated in primary care settings — strep throat, ear infections, and urinary tract infections, said Kimberly G. Blumenthal, MD, the corresponding author of the review article, in an interview.

“Inaccurate penicillin allergy labels lead to inferior clinical outcomes from using second- line treatments, which are often broad-spectrum antibiotics,” said Blumenthal, an allergist/immunologist and clinical researcher at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School, Boston. “Patients with unconfirmed penicillin allergy labels have an increased risk of treatment failures, healthcare-associated infections, and colonization or infection with resistant organisms,” she added.

Proactively de-labeling patients with unverified penicillin allergies will improve their future care as they will be able to receive first-line treatments in times of need, said Blumenthal.

“Awareness of the importance of penicillin allergy de-labeling does seem to be increasing in primary care, but barriers exist for implementing de-labeling practices outside of allergy specialist clinics,” Blumenthal told Medscape Medical News. More work is needed to increase penicillin allergy de-labeling by generalists, potentially through the use of electronic health records or other decision tools and algorithms to assess patients, she said.

Barriers to increased de-labeling in primary care include limited time, productivity targets, and pressure to achieve quality metrics for chronic health diseases, Blumenthal said. “Additionally, primary care physicians report that they lack allergy knowledge and lack the resources needed for penicillin allergy evaluations,” she said. “Potential solutions to these barriers include having a dedicated penicillin allergy de-labeling clinic, including questions on penicillin allergies during annual visits, and increasing education related to penicillin allergy de-labeling for generalists,” Blumenthal noted.

Clinician’s Guide to De-Labeling 

The use of simple allergy history tools can go a long way toward de-labeling a penicillin allergy, Blumenthal told Medscape Medical News. “Many penicillin allergy labels lack a reaction or should not be there at all and warrant de-labeling based on history alone,” she said. For example, a patient who has subsequently taken penicillin with no reaction or had only a family history of penicillin allergy is a candidate for de-labeling, she said.

For individuals who may have an allergy, risk stratification tools such as PEN-FAST can identify low-risk patients who are suitable for de-labeling in primary care, Blumenthal said. “A patient with a PEN-FAST score of 0, in my opinion, would be appropriate for primary care de-labeling in the US. Higher-risk patients can be referred to allergy specialists,” she added.

The 2023 article contains a more detailed explanation of the de-labeling process, which can be done in a few hours’ time and at relatively low cost, according to the authors.

Safely Ruling Out the Allergy

The majority of patients who are labeled as allergic to penicillin are, in fact, not allergic, said John Kelso, MD, in a presentation on allergies at the annual meeting of the American College of Physicians (ACP), previously reported by Medscape Medical News. Patients labeled as penicillin-allergic but who have no history of severe cutaneous adverse reactions are candidates for de-labeling, Kelso said.

“Many patients go through their entire lives unable to receive the best treatment for infections because they are mislabeled as being allergic to penicillin,” he emphasized.

An intradermal skin test can confirm or rule out a penicillin allergy for patients who experienced hives after a first dose of a new course of penicillin, but blood tests are not reliable, Kelso said in his ACP presentation.

De-labeling has increased dramatically in the last few years, both in allergist offices and in primary care settings, driven in part by campaigns from the American Academy of Allergy, Asthma, and Immunology; American College of Allergy, Asthma, and Immunology; the Centers for Disease Control and Prevention; and the Infectious Diseases Society of America, Kelso told Medscape Medical News.

Clinicians often assume that the process of de-labeling a penicillin allergy is “complicated, time-consuming, and dangerous,” but that is not the case, Kelso said.

To begin the de-labeling process, screen patients with appropriate questions to exclude those whose prior reaction may have been immediate anaphylaxis or a late-onset severe cutaneous adverse reaction, Kelso said in an interview. Once such patients are excluded, the process simply involves administration of a dose of amoxicillin followed by a 1-hour observation period in the clinic and asking the patients to report any late onset reactions that might develop over the next day or two, he said.

A large body of research exists to support de-labeling of penicillin allergies, Kelso told Medscape Medical News. “Perhaps the most important finding is that 95% of patients who are labeled as being allergic to penicillin are not, either because the original reaction was coincidental or the allergy has been lost over time; thus, the vast majority of patients who undergo an amoxicillin challenge for penicillin de-labeling will do so uneventfully,” he noted. “Once an appropriate history has been taken to exclude the patients who may be at risk of a more severe reaction, the remainder should be offered the de-labeling by amoxicillin challenge so that in the future they can offered the most appropriate treatment,” he said.

The review article was supported by the Massachusetts General Hospital Department of Medicine Transformative Scholar in Medicine. Blumenthal disclosed receiving a grant from Thermo Fisher Phadia Ab, receiving royalties or patent beneficiary from UpToDate, and serving as a consultant to Publix Supermarkets. Kelso had no financial conflicts to disclose.