Synopsis
Replace an imprecise penicillin-allergy label with a structured phenotype, distinguish intolerance from immediate or severe delayed hypersensitivity, and select safe testing or antibiotic alternatives.
- Ask which drug was taken, why, route, timing after the dose, symptoms, treatment, hospitalisation, time since reaction and subsequent beta-lactam tolerance.
- Nausea, diarrhoea, headache, family history or an unknown childhood label is not equivalent to IgE-mediated allergy, although uncertainty still needs safe documentation.
- Immediate urticaria, angio-oedema, bronchospasm or hypotension suggests an immediate hypersensitivity phenotype; severe blistering, mucosal or organ injury indicates a high-risk delayed reaction.
- Do not perform an unsupervised test dose. Skin testing and direct oral challenge require a risk-stratified specialist or locally governed pathway with rescue capability.
- Document the specific culprit and phenotype rather than 'penicillin allergy', and update both prescribing and primary-care records after specialist testing.
- De-labelling can restore narrower first-line treatment and reduce broad-spectrum exposure, but patient safety and shared understanding take priority over label removal targets.
Key red flags
Rapid urticaria, angio-oedema, wheeze, throat symptoms, hypotension or collapse after a beta-lactam suggests IgE-mediated or other immediate allergy.
Mucosal involvement, blistering, skin pain, facial oedema, eosinophilia, hepatitis, nephritis or systemic illness suggests a severe cutaneous or organ reaction.
Investigation priorities
Classify culprit, timing, symptoms, severity, treatment and subsequent tolerance before choosing any test.
Management branches
A patient reports penicillin allergy when antibacterial treatment is being considered.
- Ask exact drug, indication, dose-to-symptom timing, manifestations, treatment, admission and later tolerated beta-lactams; examine current reaction if present.
- Classify as likely intolerance, low-risk uncertain, immediate hypersensitivity or severe delayed reaction and record uncertainty explicitly.
- Choose infection treatment from severity and the phenotype, consulting microbiology when avoiding beta-lactams materially compromises efficacy or spectrum.