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. Any person experiencing an allergic reaction should be monitored, although monitoring may occur at home in many cases.
Symptoms develop rapidly, often within seconds or minutes.
Angioedema in the throat may be severe enough to block the airway. The pulse is rapid, and blood pressure may be low. Weakness , pale skin , heart arrhythmias , mental confusion , and other symptoms may indicate shock. CPR and other lifesaving measures may be required. This opens the airways and raises the blood pressure by constricting blood vessels.