SYSTEMIC ANAPHYLAXIS AND ANAPHYLACTOID REACTIONS
Systemic anaphylaxis represents the clinical manifestation of type I hypersensitivity that occurs when a specific antigen and a homocytotrophic antibody interact. The reaction can be sudden and progress rapidly, often without a clear cause. Death can occur because of vascular collapse or airway obstruction. The term anaphylaxis is derived from the Greek ana, meaning backward, and phylaxis, meaning protection. Poiter and Richet coined the term in 1902 after sea anemone antigen injected into a previously tolerant dog caused a fatal reaction instead of the expected immunological protection, or prophylaxis.