What You Need to Know About Anaphylaxis

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Anaphylaxis, also called anaphylactic shock, is a life-threatening systemic reaction to an environmental trigger such as an allergen. Its onset is extremely rapid, occurring within minutes or even seconds of exposure to the trigger; it is very rare for anaphylactic shock to occur more than thirty minutes after the exposure (Mayo Clinic, 2008).

Symptoms of Anaphylaxis

Anaphylaxis may begin with relatively benign symptoms such as a tingling or itching sensation or a metallic taste in the mouth. Skin symptoms such as hives, flushing, or pale skin are almost always present. The lips and/or airway commonly swell, leading to difficulty breathing; blood pressure may drop precipitously; and the heart rate may increase (tachycardia). These are the symptoms that so often make anaphylactic shock a deadly condition. Other symptoms may include gastrointestinal complaints (nausea, vomiting, diarrhea) and dizziness or fainting. (Mayo Clinic, 2008; FAAN, 2006.)

About 20% of anaphylactic reactions are biphasic, meaning they occur in two stages. In a biphasic reaction, several hours after the victim recovers from the first reaction, he or she experiences another one that is very likely to include respiratory distress (FAAN, 2006).


In most cases, anaphylaxis is an extreme allergic reaction. Certain allergens are more likely to cause anaphylactic shock than others; these include insect venom (bee, wasp, or ant stings), foods (peanuts, shellfish, etc.), latex, and medications (FAAN, 2006). Less commonly, anaphylactic shock may occur due to exercising within several hours of eating certain foods (food-dependent exercise-induced anaphylaxis) (FAAN, 2006) or may be caused by a non-allergic reaction to aspirin, NSAID drugs, or radiological contrast dyes (Mayo Clinic, 2008). Rarely, anaphylaxis is idiopathic (FAAN, 2006).

Who is at Risk?

Though this condition can affect people of any age, the group at highest risk for anaphylaxis is teens with food allergies and asthma, according to research. This is probably because teens are more likely to eat out and are less likely to recognize symptoms or carry medications (FAAN, 2006). Any person who has experienced an anaphylactic reaction in the past is at risk of experiencing another one. Even if they have never suffered anaphylaxis before, people with allergies, especially those with a combination of food allergies and asthma but also those with hay fever or hives (uticaria), have a significant risk of anaphylaxis (FAAN, 2006).


Treatment for anaphylactic shock involves treating the acute life-threatening symptoms. Epinephrine (adrenaline) should immediately be administered intravenously (Mayo Clinic, 2008). Those who know they are at risk often carry a prescription epinephrine injector (Epipen and Twinject are two common brands) for use in case of an attack. Emergency medical care should always be sought, even if an epinephrine injection causes symptoms to abate, because the injections wear off quickly and because of the possibility of a biphasic reaction.

In the long term, if the risk of anaphylaxis is due to an insect sting allergy, the allergy can be treated through allergy shots. The only way to prevent food-allergy anaphylaxis, however, is to avoid the food that causes the allergic reaction, since allergy shots cannot cure food allergies.


  • Mayo Clinic staff, 2008. “Anaphylaxis.” MayoClinic.com.
  • The Food Allergy and Anaphylaxis Network (FAAN), 2006. “Anaphylaxis.” Foodallergy.org.