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Allergies Health Center

Understanding Anaphylaxis -- the Basics

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What Is Anaphylaxis?

Anaphylaxis is a sudden, severe allergic reaction. It's a medical emergency.

Most people with allergies never have anaphylaxis. But when it happens, it works like this:

Within minutes or hours of being exposed to your allergy trigger, your body starts a chain reaction that temporarily widens your blood vessels, which can lower your blood pressure. You may pass out. You may get hives and swelling, especially around your face and throat. You may have trouble breathing, talking, or swallowing.

What Causes Anaphylaxis?

The most common causes of anaphylaxis are:

  • Foods, including peanuts and tree nuts
  • Fish and shellfish
  • Dairy products
  • Eggs
  • Insect stings, such as those from wasps, bees, and insect bites such as from ants
  • Latex
  • Medications

In some cases, anaphylaxis can also be caused by exercise, usually after eating certain foods that trigger your allergy.

Call 911

Call 911 immediately for any possible case of anaphylaxis.

An injection of epinephrine (Auvi-Q or EpiPen) can delay symptoms. If a doctor has prescribed an auto-injector for you, carry two at all times. These injections are not a cure, though they may give you more time that could be life-saving. The epinephrine quickly narrows blood vessels, stops swelling in the throat and face, and opens airways to help breathing.

Because anaphylaxis can happen so fast, always take the first signs of reaction seriously. Use an Auvi-Q or EpiPen first and then call 911 immediately.

WebMD Medical Reference

Reviewed by Luqman Seidu, MD on March 16, 2014

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