see also:

• allergy and hypersensitivity reactions
• urticaria

• serum sickness is a Gell & Coombs Type III delayed onset hypersensitivity reaction
• it is mediated by immune complexes (IgG/IgM)
• Ab-Ag complexes in circulation in ratio 1-2:1 may cause deposition onto cell membranes activating complement
• this causes local inflammation including urticaria with joint effusions
• symptoms can take as long as fourteen days after exposure to appear
• the term serum sickness–like reaction (SSLR) is occasionally used to refer to similar illnesses that arise from the introduction of certain non-protein substances

• cefaclor cephalosporins is a common cause in children
• large doses of parenteral non-human protein administration is also a common cause
  • eg. polyvalent snake bite antivenoms
• other medications

• rashes
• pruritus
• joint pain (arthralgia) +/- effusions
• fever
• lymphadenopathy
• malaise
• may cause:
  • hypotension and even shock
  • splenomegaly
  • glomerulonephritis and proteinuria

• cease trigger
• if severe, consider corticosteroids
• most will settle within 4-5 days of ceasing trigger