Notes:

10% of the population has a documented penicillin allergy

Figures for true allergy range from 10%-20% of those with a documented penicillin allergy i.e. 1-2% of the population

Remaining 8-9% of the population with a documented penicillin allergy have had an adverse or coincidental reaction in the past

True Penicillin reactions

Immediate: within 30mins to 2 hours

IgE mediated: hypersensitivity reactions: anaphylaxis, angioedema, urticaria

Delayed: >72 hours

Cytotoxic: drug-induced haemolytic anaemia, thrombocytopenia, granulocytopenia

Immune complex: serum sickness-like syndrome: fever, rash, lymphadenopathy, arthralgia

T-cell mediated: delayed maculopapular rash, allergic contact dermatitis, acute interstitial nephritis, drug-induced hepatitis, Steven Johnstone syndrome, toxic epidermal necrolysis

Patients with immediate hypersensitivity reactions or severe delayed reactions should avoid penicillins

Investigations:

Testing according to The British Society for Allergy and Clinical Immunology (BSACI):

‘Multiple antibiotic allergy’ label

Personal Hx of beta-lactam hypersensitivity in people requiring frequent antibiotics e.g. bronchiectasis, CF, immunodeficiencies, hypo/asplenia

Beta-lactam hypersensitivity and requirement for treatment with a specific beta-lactam

Hx of anaphylaxis during general anaesthetic when penicillin was given alongside other drugs