Anaphylaxis is a serious generalized or systemic hypersensitivity reaction that is rapid in onset and potentially fatal.
Diagnosis can be made if it is acute in onset of minute to several hour
duration that involves the skin, mucosal tissue or both plus having
signs & symptoms either respiratory or cardiovascular compromise.
It involves immunological response with IgE, IgG or immune complexes.
Non-immunological mechanisms are also involved and termed as nonallergic
anaphylaxis that is relatively uncommon in children.
Protracted, severe anaphylaxis are reactions occurring up to 32 hours despite aggressive management.