Rapidity of onset is a key differentiator. With fainting, the subject changes from a normal to an unconscious state within seconds. Fainting is sometimes accompanied by brief clonic seizure activity but this generally requires no specific treatment or investigation. Rarely is unconsciousness the sole manifestation of anaphylaxis. Anaphylaxis usually begins a few minutes after injection of the offending substance and is usually evident within 15 minutes.
Cardiovascular collapse can occur without respiratory symptoms.
Early recognition and treatment of anaphylaxis is vital. Measures outlined here are appropriate for initial management in non-hospital settings. Establish an oral airway if necessary. Release for 1 minute every 3 minutes. The subcutaneous route of epinephrine injection is appro-priate for mild or early cases.