Understanding Penicillin Allergies and Treatment Decisions

Contributor: Geoff Hogan MD

Educational Pearls:

• Penicillin allergies are relatively uncommon despite their frequent reports

• 10% of the population reports a penicillin allergy but only 5% of these cases are clinically significant

• 90-95% of patients may tolerate a rechallenge after appropriate allergy evaluation

• Penicillin Allergy Decision Rule (PEN-FAST) on MD Calc

• Useful tool to assess patients for penicillin allergies

• Five years or less since reaction = 2 points (even if unknown)

• Anaphylaxis or angioedema OR Severe cutaneous reaction = 2 points 

• Treatment required for reaction (e.g. epinephrine) = 1 point (even if unknown)

• A score of 0 on PEN-FAST indicates a less than 1% risk of a positive penicillin allergy test

• A score of 1 or 2 indicates a 5% risk of a positive penicillin allergy test

• A low score on PEN-FAST should prompt clinicians to proceed with the best empiric antibiotic for the patient’s infection

References

1. Broyles AD, Banerji A, Barmettler S, et al. Practical Guidance for the Evaluation and Management of Drug Hypersensitivity: Specific Drugs [published correction appears in J Allergy Clin Immunol Pract. 2021 Jan;9(1):603. doi: 10.1016/j.jaip.2020.10.025.] [published correction appears in J Allergy Clin Immunol Pract. 2021 Jan;9(1):605. doi: 10.1016/j.jaip.2020.11.036.]. J Allergy Clin Immunol Pract. 2020;8(9S):S16-S116. doi:10.1016/j.jaip.2020.08.006

2. Piotin A, Godet J, Trubiano JA, et al. Predictive factors of amoxicillin immediate hypersensitivity and validation of PEN-FAST clinical decision rule [published correction appears in Ann Allergy Asthma Immunol. 2022 Jun;128(6):740. doi: 10.1016/j.anai.2022.04.005.]. Ann Allergy Asthma Immunol. 2022;128(1):27-32. doi:10.1016/j.anai.2021.07.005

3. Shenoy ES, Macy E, Rowe T, Blumenthal KG. Evaluation and Management of Penicillin Allergy: A Review. JAMA. 2019;321(2):188-199. doi:10.1001/jama.2018.19283

4. Trubiano JA, Vogrin S, Chua KYL, et al. Development and Validation of a Penicillin Allergy Clinical Decision Rule. JAMA Intern Med. 2020;180(5):745-752. doi:10.1001/jamainternmed.2020.0403

Summarized & edited by Jorge Chalit, OMS3

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