antibiotic allergies

Antimicrobial Stewardship (AMS)

System-wide approach to promote judicious antimicrobial use; preserves effectiveness and combats resistance

Hypersensitivity (Allergy)

Immunologically mediated adverse reaction; can be immediate or delayed; IgE or cell-mediated

Intolerance

Pharmacological or individual susceptibility reaction; not immune-mediated (e.g. GI upset, headache)

Side Effect

Predictable pharmacological effect; unrelated to therapeutic action; usually mild

Adverse Drug Reaction (ADR)

Any unwanted or harmful effect from medication; includes allergy, intolerance, side effects

Antibiotic Allergy Label Consequence

Broader/more expensive antibiotics used; higher infection risk; longer hospital stays; increased cost

Penicillin Allergy History Key Questions

Which drug? Reaction nature? Timing? Severity? Time since event? Tolerated other beta-lactams since?

Immediate Hypersensitivity

Onset <1 hour; IgE-mediated; anaphylaxis, urticaria, angioedema, hypotension

Delayed Hypersensitivity

Onset >1 hour; T-cell mediated; rash, fever, organ involvement; e.g. SJS/TEN

Penicillin Cross-Allergy Basis

Shared R1 side-chain structure; cephalosporins with identical side-chain = higher risk

PPL (Polyvalent Penicilloyl Polylysine)

Major penicillin antigenic determinant; primary trigger for allergic reactions

PEN-FAST Score

5-year rule + anaphylaxis/SCAR + treatment needed; higher score = higher true allergy risk

Direct Oral Penicillin Challenge

Gold-standard de-labelling test; single dose under observation; confirm or rule out allergy

Fluoroquinolone Safety Alert

MHRA restriction — only use if other antibacterials unsuitable; tendon, neurological, psychiatric risks

C. difficile Risk Ranking

Highest — clindamycin, cephalosporins, fluoroquinolones; Lowest — gentamicin, linezolid, doxycycline

De-Labelling

Removing incorrect allergy label; restores penicillin access; narrows spectrum; improves outcomes

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