Most Penicillin Allergy Labels Are Wrong, and Doctors Are Finally Removing Them

Roughly one in ten patients carries a penicillin allergy label in their medical record, yet the overwhelming majority of these people are not truly allergic. A narrative review published in the Journal of General Internal Medicine argues that this mismatch between what the record says and what the immune system actually does has become one of the most consequential and fixable problems in modern antibiotic prescribing. The review, led by researchers affiliated with the New York Institute of Technology College of Osteopathic Medicine and NYU Grossman Long Island School of Medicine, synthesizes the epidemiology, immunology, and practical delabeling strategies that are now reshaping antimicrobial stewardship programs worldwide.

The clinical consequences of an unverified allergy label are far larger than most patients and clinicians realize. When a penicillin allergy is documented, prescribers routinely abandon beta-lactam antibiotics, the workhorse class that includes penicillins, cephalosporins, and carbapenems, in favor of broader-spectrum alternatives such as fluoroquinolones or vancomycin. Those substitutes are less targeted, more expensive, and more toxic. Population-based cohort research has linked documented penicillin allergy to increased risks of methicillin-resistant Staphylococcus aureus and Clostridium difficile infection, and other studies have associated the label with longer hospital stays, higher healthcare costs, and elevated rates of surgical site infection when prophylactic antibiotics must be swapped for inferior options.

Immunologically, true penicillin allergy is an IgE-mediated or T-cell–mediated hypersensitivity to the beta-lactam ring or its side chains. IgE-mediated reactions can produce urticaria, angioedema, bronchospasm, and anaphylaxis, typically within minutes to hours of exposure. T-cell–mediated delayed reactions, including maculopapular exanthems and severe cutaneous adverse reactions such as Stevens-Johnson syndrome, emerge days after drug exposure. But the review emphasizes that most reported reactions are not immune-mediated at all. Common culprits include viral exanthems in children misattributed to the antibiotic, gastrointestinal intolerance, and side effects such as nausea that have nothing to do with allergy. Many patients also outgrow their childhood reactions over decades, yet the label persists indefinitely in the electronic health record.

Cross-reactivity data further weaken the case for reflexive avoidance. Systematic reviews and meta-analyses have quantified cross-reactivity between penicillins and cephalosporins at low rates, driven largely by shared side chains rather than the beta-lactam core itself. Cross-reactivity with carbapenems is even lower. This means that even patients with confirmed penicillin allergy can often tolerate carefully selected cephalosporins, and the blanket avoidance of entire antibiotic classes is scientifically unjustified in most cases.

The PEN-FAST clinical decision rule represents a major advance in identifying which patients can be safely and rapidly evaluated. Developed and validated by Trubiano and colleagues, the rule assigns points for five features: facial swelling, anaphylaxis, severe cutaneous adverse reactions, the timing of the reaction within one hour of drug exposure, and treatment required for the reaction. Low-risk patients, defined by low scores, can proceed directly to oral challenge without skin testing. The rule’s simplicity means it can be applied by nonallergy specialists, including hospitalists, pharmacists, and primary care clinicians, dramatically expanding the workforce capable of delabeling.

The PALACE randomized clinical trial provided the strongest evidence yet that streamlined evaluation is safe. In this multicenter trial, low-risk adults were randomized to direct oral penicillin challenge or to traditional skin testing followed by challenge. The direct challenge approach was noninferior to skin testing, with very low rates of adverse reactions in both arms. The finding upends the conventional assumption that skin testing must always precede oral exposure, and it removes a major logistical barrier, since skin testing requires trained personnel, specialized reagents, and multiple visits that many health systems cannot provide.

Delabeling programs have now been implemented at the level of entire hospitals with measurable results. The Penicillin Allergy Delabeling Program, a multicenter whole-of-hospital intervention, demonstrated that systematic assessment and removal of inaccurate labels changes prescribing patterns. Pharmacist-led programs in tertiary care hospitals have successfully delabeled large numbers of inpatients, and systematic reviews and meta-analyses confirm that interventions delivered by nonallergy specialists are effective in both adult and pediatric populations. Economic evaluations suggest that penicillin allergy testing is cost-saving, offsetting the expense of evaluation through reduced use of broader-spectrum agents and fewer complications.

Electronic health record tools are emerging as a scalable frontier for delabeling. Clinical decision support systems, including an Allergy Fact Checker evaluated in a mixed-methods study, can flag inconsistent or low-risk allergy labels at the point of care and prompt clinicians to reassess them. These digital tools promise to embed delabeling into routine workflows rather than relying on opportunistic conversations, and they align with guidance from the American Academy of Allergy, Asthma and Immunology that penicillin allergy evaluation should be performed proactively rather than waiting for patients to request it.

The review’s practical recommendations center on integrating delabeling into antimicrobial stewardship programs, which are already mandated in most hospitals under guidelines from the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America. Stewardship teams can incorporate allergy assessment into admission workflows, prioritize patients facing imminent surgical procedures or serious infections where beta-lactams are first-line therapy, and use PEN-FAST to stratify risk before referral. The authors frame the evidence-practice gap as the central remaining challenge: the science is settled enough to act, but health systems have been slow to operationalize it.

For patients, the message is equally direct. A penicillin allergy label recorded decades ago, often in childhood, deserves reevaluation rather than lifelong deference. Removing an inaccurate label restores access to safer, narrower, and cheaper antibiotics, reduces the risk of resistant infections, and improves surgical prophylaxis. As delabeling evidence accumulates and digital tools mature, the review suggests that the era of treating an unverified allergy as a permanent diagnosis is coming to an end, and that closing this gap may be one of the highest-yield interventions available to modern antimicrobial stewardship.

Subject of Research: Penicillin allergy delabeling as an antimicrobial stewardship strategy

Article Title: Penicillin Allergy Delabeling: Bridging the Evidence-Practice Gap in Antimicrobial Stewardship

Article References: Raja, M., Patel, K., Krish, P., & Azam, Z. (2026). Penicillin Allergy Delabeling: Bridging the Evidence-Practice Gap in Antimicrobial Stewardship. Journal of General Internal Medicine. https://doi.org/10.1007/s11606-026-10793-w

Image Credits: AI Generated

DOI: 10.1007/s11606-026-10793-w

Keywords: penicillin allergy, allergy delabeling, antimicrobial stewardship, beta-lactam antibiotics, PEN-FAST, PALACE trial, oral challenge, antibiotic resistance, clinical decision rule, hospital medicine, Penicillin, Allergy