Anaphylaxis is a severe allergic reaction that involves the entire body. It can result in difficult breathing, loss of consciousness and even death if not immediately treated. Anaphylaxis is a medical emergency that requires immediate medical treatment, and later follow up care by an allergist

Anaphylaxis can occur in some people after they are exposed to a substance to which they are severely allergic, called an allergen. Generally, when an anaphylactic reaction occurs, the allergen has been injected, as in the case of a bee sting, or ingested (swallowed), as in the case of medication.

Reported deaths due to anaphylaxis occur in 0.4 cases per million people in the U.S. per year. Deaths from penicillin injections may be as high as one in 7.5 million injections, and systemic allergic reactions to the venom of stinging insects such as bees, wasps, hornets, yellow jackets or fire ants can occur in up to 4% of the general U.S. population.

  • Mechanisms

Anaphylaxis is triggered the same way other allergies are: the immune system—which serves as the body’s defense against countless substances—overreacts to a substance generally considered harmless. However, for those with severe allergies, such substances can be dangerous.

As part of the immune response, antibodies, which help to capture “invaders” in the body, circulate in the bloodstream and are present in almost all bodily fluids. People who have allergies have a specific antibody called Immunoglobulin E, or IgE . When allergens first enter the body of a person predisposed to allergies, a series of reactions occurs, and allergen-specific IgE antibodies are produced. These antibodies travel and attach themselves to the surface of cells called mast cells , where they wait for their particular allergen.

The next time that allergic individual comes into contact with the allergens he or she is sensitive to, the IgE captures them and initiates the release of chemical “mediators” from the mast cells. In the case of anaphylaxis, the allergic reaction is severe and requires immediate treatment.

Similar to anaphylaxis are anaphylactoid reactions, which do not involve the immune system but can result in severe symptoms. These reactions are triggered instead by non-IgE mechanisms which directly cause the release of mediators. Anaphylactoid reactions include those in response to non-steroidal, anti-inflammatory drugs (NSAIDS) such as aspirin or ibuprofen.

  • Signs and symptoms

Anaphylaxis is a “systemic reaction,” which means that various organ systems are affected, including the skin, upper and lower respiratory tracts, cardiovascular system, eyes, uterus and bladder. Symptoms of anaphylaxis can include nausea and vomiting, abdominal cramps, hives, swelling of tissues in the lips or joints, diarrhea, itchy skin, severe anxiety or headache, sneezing and coughing, shortness of breath and wheezing. The eyes may itch, water and swell. Additional symptoms include an itchy mouth and throat, hoarseness, nasal congestion, chest pain and tightness, a feeling of warmth and flushing, redness of the skin, cramping of the uterus, or the feeling of having to urinate. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal.

  • Anaphylaxis is sometimes mistaken for other reactions, such as hyperventilation, anxiety attacks, drugs or alcohol intoxication or low blood sugar. On occasion, patients may experience anaphylactic-like symptoms, such as low-blood pressure, which are caused by another medical condition such as a heart attack or epilepsy. If you experience any unusual symptoms, call for medical help or have someone take you to an emergency room immediately. Medical personnel will provide treatment and determine the exact cause of your condition by taking a blood sample and conducting various tests, including testing for the presence of the chemical tryptase, which suggests that the symptoms are caused by an allergy.
  • Substances that trigger reactions

Several substances can cause anaphylaxis or anaphylactoid reactions. Food and food additives are the most common trigger of anaphylaxis. Foods that can trigger anaphylaxis in those with the specific allergies are cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts. Food additives such as sulfites—found in alcoholic beverages, dried fruits and vegetables, potato products, pickles and other foods—can also sometimes trigger anaphylactoid reactions, especially in those with severe asthma. The Food and Drug Administration (FDA) has banned sulfites from fresh fruits and vegetables, and foods containing sulfites must be labeled as such.

  • Another cause of anaphylaxis is stinging insect venom. Each year, many Americans are stung by stinging insects such as yellow jackets, honeybees, paper wasps, hornets or fire ants. For most, these stings bring pain and discomfort generally lasting only a few hours. Some people, however, have severe allergic reactions to stings. Approximately 50 people in the United States die from allergic reactions to insect stings each year.
  • Some drugs can trigger anaphylaxis, including antibiotics, anti-seizure medicines, muscle relaxants and certain post-surgery fluids. Blood and blood products have also been implicated.
  • Severe latex allergy, an increasingly frequent problem, can also trigger anaphylaxis. The severity of the immediate reaction depends upon the person’s degree of sensitivity and the amount of latex allergen to which he or she was exposed. The greatest danger of severe reactions occurs when latex comes into contact with moist areas of the body or internal surfaces during surgery, because more of the allergen can rapidly be absorbed into the body.
  • Occasionally, exercise can also trigger anaphylaxis. Exercise-induced anaphylaxis is characterized by general itching with or without hives (a raised, red rash), decreased blood pressure, and narrowing of the upper respiratory tract. It is usually associated with increased environmental temperatures and intense exercise. People who experience exercise-induced anaphylaxis often may not have pre-existing allergies or asthma. Oddly enough, it does not occur after every exercise session and in some cases, only occurs after eating certain foods before exercise.
  • Treatment and prevention

If you (or anyone you are with) begins experiencing severe allergy symptoms, call for medical help or go to an emergency room, where you will receive an epinephrine (adrenalin) shot and other medications, such as antihistamines or steroids, if needed. The sooner the reaction is treated, the less severe it will be. Even if you have received immediate medical treatment on site, you should be transported to a hospital for further evaluation and treatment.

If you have ever had anaphylaxis, make sure to see an allergist for follow-up evaluation and treatment. The allergist will take your medical history and conduct other tests, if needed, to determine the exact substance to which you had a severe reaction. Your allergist may also prescribe a self-injectable epinephrine shot (adrenalin) to carry with you as a short-term treatment. Learn how to self-administer the epinephrine according to your allergist’s instructions, and replace the device before the labeled expiration date. You may also want to wear a special bracelet or necklace that identifies you as having a severe allergy. These tags can also supply other important information about your medical condition.

Avoiding allergy triggers is key to preventing anaphylaxis. If you have an allergy to certain foods, avoid those specific foods. If you have reacted to medications, take oral medications rather than injections if feasible, and follow your doctor’s orders on the proper use of your prescribed medications. If you are allergic to latex, you should avoid contact with natural rubber latex products as much as possible. For severe insect allergy, avoid spending time outdoors during insect season, carry epinephrine with you, and ask about the possibility of receiving insect venom immunotherapy, or “allergy shots,” which can protect you against future allergic reactions. If you are receiving allergy shots, it is important to wait at least 20 minutes in the clinic following a shot so that if a reaction occurs, it can be promptly treated.

If you have had an anaphylactic reaction, you may want to inform family, health care workers, employers and school personnel about your severe allergy so they can watch for symptoms and help you avoid your allergy triggers. Above all, make sure to work in partnership with your allergist to ensure your safety and health.