The immune system releases antibodies . The tissues release histamine and other substances. Prolonged anaphylaxis can cause heart arrhythmias . Anaphylaxis can occur in response to any allergen . Pollens and other inhaled allergens rarely cause anaphylaxis.
Some people have an anaphylactic reaction with no identifiable cause.
Anaphylaxis occurs infrequently. However, it is life threatening and can occur at any time. Risks include prior history of any type of allergic reaction. Symptoms develop rapidly, often within seconds or minutes. Angioedema in the throat may be severe enough to block the airway.