Anaphylaxis is an acute hypersensitivity reaction with multi-organ-system involvement that can present as, or rapidly progress to, a severe life-threatening reaction. It may occur following exposure to allergens from a variety of sources including food, aeroallergens, insect venom, drugs, and immunizations.
For the purpose of background rates the definition will be limited to severe anaphylaxis involving multi-organ failure. In addition, we will differentiate between known (i.e. bee sting, drug, food etc., ANAK). and unknown (i.e. idiopathic, ANAI) precipitating triggers.