February 17, 2026

Penicillin Allergy Delabeling

16 minutes

We’ve all seen it: the patient whose chart is “flagged” with a penicillin allergy, but when you dig into the history, the story doesn’t quite add up. Maybe it was a stomach ache in the 90s, or maybe they’re just carrying a “inherited” allergy from a parent.

In this episode of EM Pulse, we sit down with ED Clinical Pharmacist Haley Burhans to discuss why these labels are more than just a nuisance—they’re a clinical liability—and how a simple tool can empower you to fix them on the fly.

The Hidden Danger of the “Safe” Choice

Choosing a non-beta-lactam antibiotic because of a questionable allergy label feels like the path of least resistance, but the data tells a different story. We explore how “playing it safe” can actually lead to:

Worse Outcomes: Why second line antibiotics often mean higher treatment failure rates.

The “Superbug” Factor: The surprising link between penicillin allergy labels and the rise of MRSA and VRE in our communities.

The C. diff Connection: Why alternative choices might be setting your patient up for a much more difficult recovery.

The Solution: The PEN-FAST Score

How do you move from “I think this might not be a true allergy” to “I am confident this antibiotic is safe”? Haley introduces the PEN-FAST score, a validated scoring tool designed to risk-stratify patients based on a few key historical questions.

The Mnemonic: We break down the PEN-FAST acronym so you know exactly which three questions to ask to risk-stratify your patient in seconds.

IgE vs. The Rest: Learn to distinguish between the “true” dangerous hypersensitivity and the delayed reactions that shouldn’t stop you from using the best drug for the job.

The “Amoxicillin Rash”: We dive into this common pediatric “gotcha.”, why many kids end up with a lifelong allergy label after a routine ear infection, and why it often has nothing to do with the drug itself.

The Bottom Line: Patients with low PEN-FAST scores are considered low risk, making an oral challenge under observation in the ED a reasonable option. Higher scores may require shared decision-making or referral.

Why the ED is the Perfect Place for a “Challenge”

Delabeling isn’t just for the allergist’s office. We argue that the Emergency Department is actually the ideal setting to challenge these allergies.

The “Oral Challenge”: Learn the practical steps for performing a trial dose in the department.

Safety First: Why your environment and expertise make you uniquely qualified to handle the “what-ifs” better than anyone else.

Key Takeaways

Question the Label: The vast majority of reported penicillin allergies are inaccurate due to patients outgrowing the allergy or misinterpreting common side effects as allergic reactions.

History is Everything: Dig deeper than just “rash.” Ask about the timing relative to the dose, specific appearance (hives vs. flat rash), and what treatment was required (epinephrine vs. antihistamines).

Use PEN-FAST: Utilize this tool to objectify the risk.

Document Tolerance: Even if you don’t fully delete the allergy label, if you successfully treat the patient with another beta-lactam (like ceftriaxone), document that tolerance clearly to aid future clinicians.

Cephalosporins are likely safe: Later-generation cephalosporins generally have very low cross-reactivity and are usually safe options even in truly allergic patients

How do you handle documented penicillin allergies? Do you use the PEN-FAST tool? Share your experience with us on social media @empulsepodcast or at ucdavisem.com

Hosts:

Dr. Julia Magaña, Professor of Pediatric Emergency Medicine at UC Davis

Dr. Sarah Medeiros, Professor of Emergency Medicine at UC Davis

Guests:

Haley Burhans, PharmD, Emergency Medicine Clinical Pharmacist at UC Davis

Resources:

PEN-FAST Score on MDCalc

Penicillin Allergy Evaluation Should Be Performed Proactively in Patients with a Penicillin Allergy Label – A Position Statement of the American Academy of Allergy, Asthma & Immunology

Staicu ML, Vyles D, Shenoy ES, Stone CA, Banks T, Alvarez KS, Blumenthal KG. Penicillin Allergy Delabeling: A Multidisciplinary Opportunity. J Allergy Clin Immunol Pract. 2020 Oct;8(9):2858-2868.e16. doi: 10.1016/j.jaip.2020.04.059. PMID: 33039010; PMCID: PMC8019188.

Yang C, Graham JK, Vyles D, Leonard J, Agbim C, Mistry RD. Parental perspective on penicillin allergy delabeling in a pediatric emergency department. Ann Allergy Asthma Immunol. 2023 Jul;131(1):82-88. doi: 10.1016/j.anai.2023.03.023. Epub 2023 Mar 27. PMID: 36990206.

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Thank you to the UC Davis Department of Emergency Medicine for supporting this podcast and to Orlando Magaña at OM Productions for audio production services.

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