Classification of ß-lactam Allergic Reactions

Type of Reaction Clinical Manifestations Usual Onset
I Immediate

(IgE - mediated) occurs upon repeat exposure

Anaphylaxis - hypotension with exposure, or two of:
  • urticaria (hives) or angioedema/laryngeal edema

  • bronchospasm or respiratory compromise

  • vomiting or cramping abdominal pain

within 1 hour (anaphylaxis) - up to 72 hours
II Cytotoxic

(IgG or IgM mediated)

Hemolytic anemia, agranulocytosis, leukopenia, thrombocytopenia > 72 hours
III Immune Complex Serum sickness (cefaclor, cefprozil), drug-induced fever, allergic vasculitis, interstitial nephritis 7-14 days
IV T-cell mediated


Contact dermatitis, exfoliative dermatitis, maculopapular or morbilliform drug eruptions > 72 hours