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Anaphylaxis Overview

Symptoms, Causes and Treatment of Anaphylaxis


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death.

Symptoms of Anaphylaxis

Anaphylaxis is a systemic allergic reaction, which means that it affects the entire body. Not everyone will have the same symptoms when experiencing anaphylaxis. Some people may experience many of these symptoms, some just a few.

Skin, Including Mouth (occurs in 10 to 20% of cases):

  • A tingly feeling or pins-and-needles feeling
  • Itchiness
  • Hives
  • Angioedema (swelling of lips, mouth, tongue, or hands)

Airways (occurs in up to 70% of cases)

GI Tract (occurs in up to 40% of cases)

  • Nausea
  • Vomiting
  • Abdominal cramps
  • Diarrhea

Heart and Circulation (occurs in up to 35% of cases)

Other symptoms may include headache, itchy, red, or watery eyes, a metallic taste in your mouth, uterine contractions and anxiety or agitation. Many people experiencing anaphylaxis report a sense that something is very wrong with their body, or even that they are about to die. The medical literature calls this sense a "feeling of impending doom."

The most dangerous symptoms are low blood pressure, breathing difficulty, and loss of consciousness (fainting), all of which can be fatal. If you are experiencing these symptoms, call 911 immediately. Waiting to see if symptoms improve may mean it is too late for help.

Causes of Anaphylaxis

Anaphylaxis is a severe allergic reaction, in which your body's immune system reacts to an allergen by producing large amounts of histamine and other "mediators" that cause allergy symptoms. It is not well understood why some people experience mild symptoms, such as a runny nose or rash, while others experience severe allergic reactions.

Major Allergens

The most common triggers for anaphylaxis are medications, insect stings, latex, and food, but they can be caused by any allergen. The most common food allergens in the United States are:

Even a very tiny portion of an allergen can trigger anaphylaxis. Cross-contamination during food preparation can introduce enough of an allergen into a safe food to cause a reaction.

You cannot predict the severity of an allergic reaction based on previous reactions. You may have anaphylaxis from eating something that in the past only gave you hives.

Anaphylaxis and Other Diseases

Some conditions that can increase the risk or severity of anaphylaxis are:

  • Asthma - Poorly controlled asthma has been linked to fatal anaphylaxis in adolescents and young adults.
  • Heart disease - Cardiovascular disease is a risk factor for fatal anaphylaxis in older adults.
  • Chronic obstructive pulmonary disease (COPD) - COPD and other diseases that make breathing difficult may increase the risk of anaphylaxis.
  • Mastocytosis - A disease that causes the body to overproduce mast cells (the cells that release histamine in an allergic reaction.)
  • Some medications may interfere with epinephrine. If you are at risk for anaphylaxis, talk to your doctor about the other medications you take.

Exercise-Induced Anaphylaxis

Exercise-induced anaphylaxis (EIA) is a perplexing problem that usually develops in adulthood. EIA may or may not involve a food allergy trigger, but people with EIA are generally able to tolerate the food allergen when they do not exercise after eating.

About 75% of the people who experience EIA are women. The most common food triggers of exercise-induced anaphylaxis are shellfish, alcohol, tomatoes, cheese and celery.

Anaphylaxis Treatment

There is no cure for anaphylaxis at this point in time. However, there is emergency treatment, which is epinephrine. An epinephrine auto-injector is a drug form of adrenaline, the fight-or-flight hormone that your body produces in emergencies. It increases heart rate and opens up your airways and blood vessels so that you can breathe better and blood can move around your body more easily.

To be effective, epinephrine must be used at the start of an anaphylactic reaction. Delay of more than 30 minutes from the beginning of symptoms has been linked with greater risk of fatal or near-fatal reactions. Between 10 and 20% of people will need a second dose of epinephrine 5 to 15 minutes after the first dose.

After using epinephrine, it is important to lie down and stay horizontal.

Antihistamines are not effective in treating anaphylaxis. If you are experiencing shortness of breath, wheezing, dizziness or fainting, an antihistamine will not be able to help your symptoms.

If you have a history of, or are at risk for anaphylaxis, your doctor will prescribe two epinephrine auto-injectors. You will need to carry both of your auto-injectors with you at all times in case of future reactions.

Emergency Preparedness

Managing food allergies and anaphylaxis means avoiding your triggers and being prepared for an emergency.

Create an Emergency Action Plan

An Emergency Action Plan (EAP) outlines the people who need to be contacted in case of an emergency, when and how different medications should be administered, and other details of handling a potential anaphylactic reaction. The Food Allergy and Anaphylaxis Network (FAAN) has a downloadable sample EAP in multiple languages.

Your EAP won't do any good if it just sits in a drawer. Share it with important people in your life, such as relatives, co-workers, and friends.

Train your Friends and Family

Your friends, family, and co-workers should all know the signs of anaphylaxis and be trained to administer your auto-injector if needed. Ask your doctor for a training auto-injector that family and friends can use to practice.

Manufacturer instructions for each type of auto-injector:

Wear a Medical ID

If you have severe food allergies, you should wear a medical ID at all times. Medical IDs can give emergency personnel the information they need when they need it.

  • Medical alert jewelry comes in a wide variety of options, from shoe tags for jogging, to handmade beaded bracelets.
  • Medic Alert is a nonprofit registration service that emergency personnel can call for information about your child.

Prevalence of Anaphylaxis

A study published in the Journal of Allergy and Clinical Immunology found that there were about 200,000 emergency room visits per year for food allergies between 2001 and 2005. About 90,000 of the 200,000 visits were for anaphylaxis. This works out to about 18,000 ER visits a year for anaphylaxis in the United States.

Researchers currently estimate that 7.8 million people in the U.S. have food allergies.


American Academy of Asthma, Allergy, and Immunology. Tips to Remember: Anaphylaxis. Accessed 1/18/2011. http://www.aaaai.org/patients/publicedmat/tips/whatisanaphylaxis.stm

Clark, S. et al. Frequency of US emergency department visits for food-related acute allergic reactions. J Allergy Clin Immunol. 2010 Dec 15.

Food Allergy and Anaphylaxis Network. Anaphylaxis. Accessed 1/18/2011. http://www.foodallergy.org/section/a

NIAID-Sponsored Expert Panel. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. The Journal of Allergy and Clinical Immunology. Volume 126, Issue 6, Supplement , Pages S1-S58, December 2010

Simons, F. Estelle. Anaphylaxis: Recent advances in assessment and treatment. The Journal of Allergy and Clinical Immunology. Volume 124, Issue 4 , Pages 625-636, October 2009

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