Definition and pathophysiology (Ann Emerg Med 2006;47:373)

  • Severe, rapid onset (mins to hrs), potentially life-threatening systemic allergic response
  • IgE-mediated mast cell degranulation with release of histamine, tryptase, and TNF
  • Precipitates systemic reactions (bronchospasm, tissue swelling, fluid shifts, vasodilation)
  • Common triggers: penicillins, cephalosporins, shellfish, nuts, insect stings, IV contrast (not truly an IgE-mediated mechanism, but clinically similar)

Diagnosis: any of the three following criteria

  1. Acute illness with skin ± mucosal involvement (rash, flushing, hives), AND at least one of:
    • Respiratory compromise (wheeze, stridor, dyspnea, hypoxemia)
    • Hypotension or hypoperfusion (syncope, incontinence)
  2. Two f the following after exposure to a