Understanding selective aminopenicillin allergy: findings from a long-term case series

This retrospective study aimed to characterize the clinical features and diagnostic outcomes of selective aminopenicillin hypersensitivity among patients evaluated for β-lactam allergy between 2018 and 2024. A total of 1,340 patients were assessed, of whom 167 (12.5%) had confirmed selective allergy to aminopenicillins, predominantly affecting middle-aged women and presenting more frequently with immediate reactions such as urticaria/angioedema and anaphylaxis. All patients underwent a standardized work-up including skin prick and intradermal tests, patch tests and/or delayed intradermal testing when indicated, specific IgE measurement in immediate reactions, and drug challenge tests (DCT) with amoxicillin or amoxicillin-clavulanic acid. Intradermal testing and DCT were the most informative procedures, whereas specific IgE contributed minimally to the diagnosis of selective aminopenicillin allergy. Notably, all patients tolerated phenoxymethylpenicillin (penicillin V) during DCT, confirming selective sensitization to the aminopenicillin side chain and supporting the safe use of other β-lactams in this population. These findings highlight the clinical relevance of selective aminopenicillin allergy and underscore the importance of comprehensive diagnostic algorithms to optimize antibiotic stewardship and expand therapeutic options for labeled β-lactam-allergic patients.