Penicillin / drug allergy delabeling pathway

Risk-stratifies a reported drug allergy (PEN-FAST), routes low-risk histories to direct oral challenge, and applies the SCAR safety rule. Links PEN-FAST and the β-lactam side-chain calculators.

Evidence tier: Guideline-derived.

Decision points

  • What is the reaction phenotype?
  • What is the risk level?
  • Challenge outcome?

Do-not-miss pitfalls

  • Do not leave a vague "penicillin allergy" label after a negative challenge, update the record and notify patient/PCP/pharmacy.
  • Do not use a negative skin/patch test to clear a SJS/TEN/DRESS patient for rechallenge, negative testing has poor NPV.
  • Do not retain the obsolete ~10% penicillin–cephalosporin cross-reactivity model; risk follows R1 side-chain similarity.
  • Do not confuse predictable side effects or vancomycin flushing with true allergy.
  • Do not globally label a single-NSAID reactor as "NSAID-allergic", cross-reactive (NERD/NECD/NIUA) and single-NSAID phenotypes differ.

Evidence & citations

  1. Khan DA, Banerji A, Blumenthal KG, et al. Drug allergy: A 2022 practice parameter update. J Allergy Clin Immunol. 2022;150(6):1333-1393. PMID 36122788
  2. Copaescu AM, Vogrin S, James F, et al. Efficacy of a Clinical Decision Rule to Enable Direct Oral Challenge in Low-Risk Penicillin Allergy (PALACE). JAMA Intern Med. 2023;183(9):944-952. PMID 37459086
  3. Trubiano JA, Vogrin S, Chua KYL, et al. Development and Validation of a Penicillin Allergy Clinical Decision Rule (PEN-FAST). JAMA Intern Med. 2020;180(5):745-752. PMID 32176248
  4. Zagursky RJ, Pichichero ME. Cross-reactivity in β-Lactam Allergy. J Allergy Clin Immunol Pract. 2018;6(1):72-81. PMID 29017833

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.