Anaphylaxis is a life-threatening type of allergic reaction.
Anaphylactic reaction; Anaphylactic shock; Shock - anaphylactic; Allergic reaction - anaphylaxis
Anaphylaxis is a severe, whole-body allergic reaction to a chemical that has become an allergen. An allergen is a substance that can cause an allergic reaction.
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. The condition 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. But, the symptoms, risk of complications, and treatment are the same for both types of reactions.
Anaphylaxis can occur in response to any allergen. Common causes include:
Pollen 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 any of the following:
Exams and Tests
The health care provider will examine the person and ask about what might have caused the condition.
Tests for the allergen that caused anaphylaxis (if the cause is not obvious) may be done after treatment.
Anaphylaxis is an emergency condition that needs medical attention right away. Call 911 immediately.
Check the person's airway, breathing, and circulation, which are known as 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.
The person may receive medicines to further reduce symptoms.
Anaphylaxis can be life-threatening without prompt treatment. Symptoms usually do get better with the right therapy, so it is important to act right away.
Without prompt treatment, anaphylaxis may result in:
When to Contact a Medical Professional
Call 911 if you or someone you know develops severe symptoms of anaphylaxis. Or, go to the nearest emergency room.
To prevent allergic reactions and anaphylaxis:
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Schwartz LB. Systemic anaphylaxis, food allergy, and insect sting allergy. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 253.
Tran TP, Muelleman RL. Allergy, hypersensitivity, angioedema, and anaphylaxis. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 119.
Review Date: 3/20/2016
Reviewed By: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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