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Anaphylaxis

Definition

Anaphylaxis is a life-threatening type of allergic reaction.

Alternative Names

Anaphylactic reaction; Anaphylactic shock; Shock - anaphylactic

Causes

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

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.

Treatment

Anaphylaxis is an emergency condition that needs 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.

  1. Call 911.
  2. Calm and reassure the person.
  3. If the allergic reaction is from a bee sting, scrape the stinger off the skin with something firm (such as a fingernail or plastic credit card). Do not use tweezers -- squeezing the stinger will release more venom.
  4. If the person has emergency allergy medicine on hand, help the person take or inject the medication. Avoid oral medication if the person is having difficulty breathing.
  5. Take steps to prevent shock. Have the person lie flat, raise the person's feet about 12 inches, and cover him or her with a coat or blanket. Do not place the person in this position if a head, neck, back, or leg injury is suspected, or if it causes discomfort.

DO NOT:

Paramedics or other health care providers may place a tube through the nose or mouth into the airways (endotracheal intubation). Or emergency surgery will be done to place a tube directly into the trachea (tracheostomy or cricothyrotomy).

The person may receive medicines to further reduce symptoms.

Outlook (Prognosis)

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.

Possible Complications


When to Contact a Medical Professional

Call 911 if you develop severe symptoms of anaphylaxis. Or have someone take you to the nearest emergency room.

Prevention


References

Lieberman PL. Recognition and first-line treatment of anaphylaxis. Am J Med. 2014;127:S6-S11.

Lieberman PL, Nicklas RA, Oppenheimer J, and the Joint Task Force on Practice Parameters of the American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology; and Joint Council of Allergy, Asthma and Immunology. The diagnosis and management of anaphylaxis practice parameter: 2010 update. J Allergy Clin Immunol. 2010;126:477-480.

Schwartz LB. Systemic anaphylaxis, food allergy, and insect sting allergy. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 261.


Review Date: 5/11/2014
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.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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