Anaphylaxis is the most severe type of allergic reaction and requires immediate medical attention. If not treated right away, anaphylaxis may cause shock or death.

What happens during anaphylaxis?

People who have allergies have higher levels of the type of antibody known as Immunoglobulin E (IgE). The anaphylactic reaction depends on previous exposure or "sensitization" to a particular allergen. During the first exposure, the body builds up allergen-specific IgE antibodies.

Upon re-exposure to the allergen, the IgE antibodies launch a whole-body (systemic) immune response. This can result in rapid loss of blood pressure. The heart may strain, and the brain may stop receiving oxygen flow. The vocal chords and other tissues may swell. The lungs can fill with fluid, and the airways may become severely constricted.

What causes anaphylaxis?

Substances that can cause anaphylaxis include:

  • Insect sting venom
  • Foods -- particularly shellfish, peanuts, other tree nuts, eggs, and milk
  • Medications -- including antibiotics, general anesthetics, insulin, and progesterone
  • Vaccines that contain egg protein
  • Latex
  • Immunotherapy solutions

People prone to anaphylaxis may have a history of food allergy, asthma, prior anaphylactic reactions, or other allergic reactions.


Anaphylaxis usually occurs rapidly, unexpectedly, and affects many parts of the body. Watch for the following symptoms:

  • Warmth, skin flushing, or hives
  • Tingling and swelling in the lips, feet, hands, or other body parts
  • Wheezing, whistling while breathing, or shortness of breath
  • Difficulty swallowing due to swelling in the throat
  • Lightheadness or faintness
  • Palpitations or irregular heartbeat
  • Loss of consciousness or seizures due to low blood pressure

Other symptoms may include hoarseness, cough, chest tightness, sneezing, and gastrointestinal symptoms like bloating, cramps, nausea, or vomiting.

Emergency treatment

Seek treatment of anaphylaxis immediately to re-open the airways and regain normal blood pressure. If you or someone you're with is experiencing symptoms of anaphylaxis, call 911 for emergency medical treatment or go directly to the nearest emergency room.

At the hospital or treatment facility, you may have a blood sample taken for a "serum tryptase test," which will distinguish anaphylaxis from other types of reactions. You will receive a shot of epinephrine, or other anti-inflammatory medications like corticosteroids or antihistamines. Your vital signs will be monitored for several hours after the reaction -- anaphylactic symptoms can persist after treatment or return hours later.

Be prepared!

Stay away from allergens that you know you're allergic to. (Allergy testing can help you to determine specific allergens to avoid.) If you have food allergies, always read food labels, and keep a food diary. When you go to a restaurant, talk to the server about the ingredients in the food before ordering. Avoid stinging insects, if you can.

If you know you're prone to anaphylaxis, wear a medical identification bracelet or necklace to alert hospital and emergency personnel. Also, tell your friends, family members, and co-workers, and write out an action plan, so they know how to respond in case of emergency.

Always carry an injectable epinephrine kit (such as EpiPen or Twinject) in case of an anaphylactic reaction -- your doctor will show you how to give yourself the intra-muscular shot of epinephrine. This medicine will help you feel better, but you still need to be under medical observation until all your vital signs are back to normal.


The diagnosis and managment of anaphylaxis: an updated practice paramater. J Allergy Clin Immunol. 2005 Mar;115(Suppl 3):S483-523.


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Review Date: 4/4/2007

Reviewed By: Alan Greene, M.D., F.A.A.P., Department of Pediatrics, Packard Children's Hospital, Stanford University School of Medicine; Chief Medical Officer, A.D.A.M., Inc.

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