Anaphylaxis: A Serious Allergic Reaction

Use epinephrine for anaphylaxis. Peter Dazeley/Getty Images

Anaphylaxis is a serious allergic reaction that involves more than one body system. It can occur within minutes to hours of exposure to a substance, such as a food or another element, like a bee sting.  When severe, and if untreated, anaphylaxis may cause death.

What Causes an Anaphylactic Reaction?

Food allergies can cause an anaphylactic reaction, especially peanuts, tree nuts (almonds, walnuts, cashews and Brazil nuts), fish, shellfish, milk, and eggs.

Non-food substances like a wasp or bee sting, natural latex (rubber), penicillin or other drugs may also cause anaphylaxis.

Symptoms of Anaphylaxis

Anaphylaxis affects the entire body. There are several symptoms associated with anaphylaxis. Not everyone will have the same symptoms when experiencing anaphylaxis. Some people may experience many of these symptoms, or some may experience just a few. They are:

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

Generalized flushing of the skin

A tingly feeling or pins-and-needles feeling


Hives (blotchy red bumps) appearing anywhere on the body

Angioedema (swelling of lips, mouth, tongue, or hands)

Airways (occurs in up to 70% of cases)



Sneezing or runny nose

Swelling of the throat and mouth

Hoarse voice or scratchy throat

Difficulty swallowing

Shortness of breath

Difficulty breathing

Severe asthma

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



Abdominal cramps


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

Rapid or slow heartbeat

Drop in blood pressure causing a sudden feeling of weakness



Looking pale or blue




Other symptoms may include headache, itchy, red, or watery eyes, a metallic taste in the 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.

Causes of Anaphylaxis

An anaphylactic reaction is caused by your immune system reacting to an allergen. Your body, upon sensing the allergen, goes into defense mode, creating a reaction to fight against the allergen. As such, a sudden release of chemical substances, including histamine, occurs from cells in the blood and tissues where they are stored. This chemical substance release places your immune system in full defense mode, causing the symptoms associated with an anaphylactic reaction. Tiny quantities of allergen can cause a reaction.

It is not understood why some people experience mild symptoms, such as a hives or swelling, and others experience more severe 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:

  • Milk
  • Peanuts
  • Shellfish
  • Tree nuts
  • Eggs
  • Fish
  • Soy
  • Wheat

Cross-contamination during food preparation can introduce enough allergen into an otherwise safe food, causing a reaction.

You cannot predict the severity of an allergic reaction based on previous reactions. If you have suffered a bad allergic reaction, then your next reaction may be more severe. If you have reacted due to allergen contact with your skin, or to a small allergen dose, this may indicate a severe reaction if exposed to a larger dose in the future. If you have asthma and allergies, you are at a higher risk for anaphylaxis.


Prevalence of Anaphylaxis

A study by the Asthma and Allergy Foundation of America (AAFA) published in the Journal of Allergy and Clinical Immunology (JACI) found that severe life-threatening allergic reactions are common in the U.S. Anaphylaxis occurs in nearly 1 out of every 50 Americans (1.6%), with an actual rate that is probably higher, closer to 1 out of every 20 Americans (5.1%).

Anaphylaxis and Other Diseases

Some medical conditions may increase the risk or severity of anaphylaxis:

  • 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 allergen trigger. People with EIA are generally able to tolerate a potential 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. Most individuals who are at risk for anaphylaxis will be prescribed emergency epinephrine in the form of an auto-injector. Epinephrine causes the blood vessels to constrict and relaxes the smooth muscles in the lungs so that breathing is easier. It also stimulates the heartbeat and helps to stop the swelling around the face and lips. If you are prone to anaphylaxis, or at risk for an anaphylactic reaction (if you have an adrenaline auto-injector you are at risk for anaphylaxis), and experience symptoms of a reaction, you shouldn’t wait to see if symptoms improve.

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 is unlikely to be effective.

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 a reaction.

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.

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.

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.


Anaphylaxis in America.

American Academy of Asthma, Allergy, and Immunology. Tips to Remember: Anaphylaxis.

Food Allergy Research and Education (FARE). Anaphylaxis.

NIAID-Sponsored Expert Panel. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. J All Clin Immun. 2010; 126 (6): S1-S58.

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