Infection-embedded penicillin allergy de-labelling delivers immediate antimicrobial stewardship gains in patients...

Unconfirmed penicillin allergy labels restrict antibiotic options and drive deviation from antimicrobial guidelines. To address this, we established an infection-embedded penicillin allergy de-labelling (PADL) service embedded within existing infection-liaison touchpoints (microbiology meetings, advice calls and infection reviews) to target patients with active infection needs.

We performed a retrospective analysis of all 189 referrals to our PADL service (March 2022 to December 2025), nested within a baseline prevalence review of 218 375 admissions. Furthermore, to quantify the clinical cost of allergy labels, we surveyed infection experts, using 20 clinical vignettes, to determine prescribing variance had de-labelling not occurred.

Of patients, 82.5% (156/189) were classified as having acute, complex or recurrent infection; 45% (85/189) were directly de-labelled, while 41.8% (79/189) were excluded by low-risk criteria prompting specialist referral for full penicillin allergy testing. Critically, for patients on active therapy, de-labelling triggered an immediate regimen change in 84.1%, driving a 43% intravenous-to-oral switch rate, a mean reduction of 0.7 antibiotics per patient and significantly reducing antibiotic spectrum coverage (P = 0.0004). Expert review of vignettes revealed only minimal concordance on alternative regimens (Fleiss' kappa 0.28) had we not de-labelled, implying that persistent labels lead to non-standardized prescribing.

Infection-embedded de-labelling is a high-yield intervention that can deliver immediate stewardship returns in patients with active infection needs. A caveat is that a significant proportion of excluded patients require specialist allergy referral, carrying resource implications and underscoring the need for careful planning with local allergy services at inception of 'low-risk' pathways.