About Anaphylaxis

What is anaphylaxis

Anaphylaxis is a serious, acute, allergic reaction that may cause death. It occurs when an allergic person is exposed to their particular allergen (a substance capable of causing an allergic reaction). When the allergen enters the body it triggers the release of chemicals that can lead to life-threatening symptoms.

The severity of an allergic reaction, as well as the symptoms, can vary from person to person and from one episode to the next in the same person.


Although the precise number of people at risk of anaphylaxis is unknown, a recent publication found that approximately 7% of Canadians self-report a food allergy.

Health Canada notes that physician-diagnosed food allergies are estimated at prevalence levels of up to 5-6% for young children and 3-4% for adults in westernized countries.

Reported food allergy is increasing among children of all ages.


Some of the more common allergen triggers are: peanuts, tree nuts, sesame seeds, soy, milk, eggs, seafood (fish, crustaceans and shellfish), mustard, wheat, and sulphites.

Other known triggers are insect stings, certain medicines, latex, and exercise (exercise-induced anaphylaxis). There are also unknown causes (idiopathic anaphylaxis).


Risk factors for anaphylaxis include:

  • A previous history of anaphylaxis
  • Asthma
  • Food allergies


Anaphylaxis affects multiple body systems: skin, upper and lower respiratory system, intestinal tract, heart and blood vessels. The most common warning symptoms of anaphylaxis are: hives and swelling.

Typical symptoms of anaphylaxis include:

  • Swelling of the throat, lips, tongue, or the area around the eyes
  • Difficulty breathing or swallowing
  • Metallic taste or itching in the mouth
  • Generalized flushing, itching, or redness of the skin
  • Stomach cramps, nausea, vomiting, or diarrhea
  • Increased heart rate
  • Decreased blood pressure
  • Paleness
  • Sudden feeling of weakness
  • Anxiety or an overwhelming sense of doom
  • Collapse
  • Loss of consciousness

At risk for anaphylaxis

The most important aspect of the management of patients with life threatening allergies is avoidance of the allergen trigger(s). But it is impractical to achieve complete avoidance of all allergenic foods as there can be hidden or accidentally introduced sources.

In the event of contact with the offending allergen, epinephrine by subcutaneous or intramuscular injection is the treatment of choice for anaphylaxis.

That’s why it is important to be prepared. Patients and caregivers should:

  • always carry and know how to use their epinephrine auto-injector
  • tell others where they keep their auto-injector in case they are unable to speak in an allergic emergency
  • wear a medical identification bracelet or necklace

What to do in an emergency

When an allergic reaction occurs, epinephrine should be administered immediately.

Research shows that most deaths from anaphylaxis have been associated with no or delayed administration of epinephrine. Patients, their family members or caregivers should keep epinephrine with them at all times. Epinephrine is the medicine in the Allerject® auto-injector.

With a severe, long-lasting allergic reaction, you may need to administer an additional dose of epinephrine. More than two sequential doses of epinephrine should only be administered under direct medical supervision.

All individuals receiving emergency epinephrine must be immediately transported to hospital, ideally by ambulance, for evaluation and observation. Following medical treatment, patients must stay within close proximity to a hospital or where they can call 911 for the next 48 hours.

For more information, see Frequently Asked Questions.