Your immune system produces antibodies that defend against foreign substances. This is good when a foreign substance is harmful (such as certain bacteria or viruses). But some people's immune systems overreact to substances that shouldn't cause an allergic reaction. When this occurs, the immune system sets off a chemical chain reaction, leading to allergy symptoms. Normally, allergy symptoms aren't life-threatening. But some people have a severe allergic reaction that can lead to anaphylaxis. Even if you or your child has had only a mild anaphylactic reaction in the past, there's still a risk of more severe anaphylaxis.

A number of allergens can trigger anaphylaxis, depending on what you're allergic to.

Common anaphylaxis triggers include:

  • Certain medications, especially penicillin
  • Foods, such as peanuts, tree nuts (walnuts, pecans, almonds, cashews), wheat (in children), fish, shellfish, milk and eggs
  • Insect stings from bees, yellow jackets, wasps, hornets and fire ants

Less common causes of anaphylaxis include:

  • Latex
  • Medications used in anesthesia
  • Exercise

Anaphylaxis symptoms are sometimes caused by aspirin and other drugs — such as ibuprofen (Advil, Motrin, others) and naproxen (Aleve, Midol Extended Relief) — and the intravenous (IV) contrast used in some X-ray imaging tests. Although similar to allergy-induced anaphylaxis, this type of reaction isn't triggered by allergy antibodies.

Anaphylaxis triggered by exercise is not common and varies from person to person. In some people, aerobic activity, such as jogging, triggers anaphylaxis. In others, less intense physical activity, such as walking, can trigger a reaction. Eating certain foods before exercise or exercising when the weather is hot, cold or humid also has been linked to anaphylaxis in some people. Talk with your doctor about any precautions you should take when exercising.

If you don't know what triggers your allergy attack, your doctor may do tests to try to identify the offending allergen. In some cases, the cause of anaphylaxis is never identified. This is known as idiopathic anaphylaxis.

Jan. 16, 2013

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