A hypersensitivity reaction consisting of fever, rashes, joint pain and glomerulonephritis, resulting from localization of circulating, soluble, antigen-antibody complexes, which induce inflammatory reactions. Serum sickness was originally induced following therapy with large doses of antibody from a foreign source - e.g. horse serum.
Serum sickness is a reaction to an antiserum derived from an animal source. It is a type of hypersensitivity, specifically immune complex (type 3) hypersensitivity. Serum sickness typically develops up to ten days after exposure to the antiserum, and symptoms are similar to an allergic reaction.