Anaphylaxis is a life-threatening type of allergic reaction.
Anaphylactic reaction; Anaphylactic shock; Shock - anaphylactic
Anaphylaxis is a severe, whole-body allergic reaction to a chemical that has become an allergen. After being exposed to a substance such as bee sting venom, the person's immune system becomes sensitized to it.
When the person is exposed to that allergen again, an allergic reaction may occur. Anaphylaxis happens quickly after the exposure, is severe, and involves the whole body.
Tissues in different parts of the body release histamine and other substances. This causes the airways to tighten and leads to other symptoms.
Some drugs (morphine, x-ray dye, aspirin, and others) may cause an anaphylactic-like reaction (anaphylactoid reaction) when people are first exposed to them. These reactions are not the same as the immune system response that occurs with "true" anaphylaxis. However, the symptoms, risk for complications, and treatment are the same for both types of reactions.
Anaphylaxis can occur in response to any allergen. Common causes include:
Pollens and other inhaled allergens rarely cause anaphylaxis. Some people have an anaphylactic reaction with no known cause.
Anaphylaxis is life-threatening and can occur at any time. Risks include a history of any type of allergic reaction.
Symptoms develop quickly, often within seconds or minutes. They may include the following:
The health care provider will wait to test for the allergen that caused anaphylaxis (if the cause is not obvious) until after treatment.
Anaphylaxis is an emergency condition that needs professional medical attention right away. Call 911 immediately.
Check the person's airway, breathing, and circulation (the ABC's of Basic Life Support). A warning sign of dangerous throat swelling is a very hoarse or whispered voice, or coarse sounds when the person is breathing in air. If necessary, begin rescue breathing and CPR.
Paramedics or other health care providers may place a tube through the nose or mouth into the airways (endotracheal intubation) or perform emergency surgery to place a tube directly into the trachea (tracheostomy or cricothyrotomy).
The person may receive antihistamines, such as diphenhydramine, and corticosteroids, such as prednisone, to further reduce symptoms (after lifesaving measures and epinephrine are given).
Anaphylaxis is a severe disorder that can be life-threatening without prompt treatment. However, symptoms usually get better with the right therapy, so it is important to act right away.
Call 911 if you develop severe symptoms of anaphylaxis. If you are with another person, he or she may take you to the nearest emergency room.
Schwartz LB. Systemic anaphylaxis, food allergy, and insect sting allergy. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 261.
Wasserman SI. Approach to the person with allergic or immunologic disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 257.