What is anaphylaxis?

Anaphylaxis is a serious and potentially life-threatening allergic reaction. Normally, when you are allergic to a substance, the body’s immune system overreacts by releasing chemicals. These chemicals cause the annoying symptoms — itchy, watery eyes, runny nose — of an allergy.

However, in some people, this reaction is much more severe, and anaphylaxis is the result. Symptoms of anaphylaxis may include swelling, hives, lowered blood pressure, shortness of breath, wheezing, and difficulty swallowing.

In these cases, a person can go into anaphylactic shock. Blood pressure drops severely and swelling occurs in the bronchial tissues, causing symptoms of choking and loss of consciousness. If anaphylactic shock isn't treated immediately, it can be fatal.

What are the most common causes of anaphylaxis?

Food allergy is a recognized cause of anaphylaxis. Foods that may cause anaphylaxis include:

  • Peanuts
  • Tree nuts (for example, walnuts, hazelnuts, Brazil nuts, cashews, etc.)
  • Shellfish (for example, shrimp, lobster, etc.)
  • Cow's milk
  • Egg
  • Wheat
  • Soy

Venom allergies (for example, allergy to bee or wasp stings) can also cause anaphylaxis.

Some substances can cause reactions, called anaphylactoid reactions, that are similar to and just as serious as anaphylaxis. Aspirin, other nonsteroidal anti-inflammatory drugs, and dye given for CT scans can cause these reactions.

Pollens and other inhaled allergens (allergy-causing substances) rarely cause anaphylaxis.

What are the symptoms of anaphylaxis?

Anaphylaxis may begin with severe itching of the eyes or face. Within minutes, it can move on to more serious symptoms, including:

If you have symptoms of anaphylaxis, get medical help immediately. The condition can quickly cause increased heart rate, sudden weakness, a drop in blood pressure, shock, and ultimately unconsciousness and even death.

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