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 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.

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.

How is anaphylaxis diagnosed?

Anaphylaxis is diagnosed based on its symptoms. People with a history of allergic reactions may have a greater risk for developing a severe reaction in the future.

Skin testing and blood tests may help confirm the substances that cause severe allergic reactions. If anaphylactic reactions are suspected, testing should be done under the guidance of an allergy specialist.

How is anaphylaxis treated?

The only effective treatment for acute anaphylaxis is epinephrine (adrenaline) by injection (shot). Epinephrine works quickly to reverse anaphylactic symptoms. The patient can give him- or herself an epinephrine injection. The most common spot to inject is the thigh.

If you are near someone who is going into anaphylactic shock, call for professional medical help immediately. CPR and other lifesaving measures may be needed.

If the person cannot breathe, medical professionals may have to place a tube through the nose or mouth into the airway or even perform emergency surgery (tracheostomy) to place a tube directly into the trachea (windpipe).

In addition to epinephrine, treatment for shock includes intravenous fluids and medications to support the actions of the heart and circulatory system. After a person in shock is stabilized, he or she may receive antihistamines and corticosteroids to further reduce symptoms.

Living with allergies

If you are allergic to bee stings or anything that causes anaphylaxis, you should always be prepared. Carry an epinephrine injection kit with you at all times. Also, if you have any drug allergies, you should always tell your health care provider before having any type of treatment, including dental care. It is also a good idea to either wear jewelry or carry a card that identifies your allergy. In cases of emergency, it could save your life.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 3/28/2016.... #8619