Common Causes


The following are the most common food allergens in Canada. Click on the links below for more information on each allergen.

Peanut Soy
Egg Sesame seeds
Milk Seafood (fish, crustaceans, shellfish)*
Tree nuts (e.g. almond, cashew, hazelnut, pistachio) Sulphites
Wheat Mustard

These are identified as "priority allergens" by Health Canada. It is important to recognize that this is not an exclusive list. Although the priority allergens have been known to cause 90% of allergic reactions, any food can trigger a reaction.

The information provided for the above allergens has been excerpted from Anaphylaxis Canada's Allergen Cards and Health Canada's pamphlets on priority allergens.

*For regulatory purposes, Health Canada uses the following terms to describe food from the sea: fish, shellfish (e.g. oysters, clams) and crustaceans (e.g. lobster, shrimp).


An allergy to medication happens when your immune system reacts to the drug. Many different drugs can cause an allergic reaction, including prescription and over-the-counter drugs. Reactions to a medication usually happen within an hour of taking the drug but can occur much later. You can also develop an allergic reaction to a medication after you've been taking it for several weeks. It is important to know the names of the drugs that you are allergic to and avoid them.

Here are some tips to stay safe:
  • Tell all of your healthcare providers about your drug allergy.
  • Wear a MedicAlert® bracelet so that people will know about your allergy if you are in an accident.
  • Talk to your doctor if you have a reaction to a drug or if you have any signs or symptoms of an allergic reaction. Your doctor may be able to replace your medication with another drug that won't cause a reaction.

Insect Stings

Insect stings from honeybees, bumblebees, yellow jackets, hornets, wasps, and fire ants are the most common trigger of insect sting allergy. Symptoms of a reaction usually start immediately after a sting. Having one type of reaction doesn't mean you'll always have the same reaction every time you're stung.

To reduce the risk of being stung:
  • Do not wear perfumes or use shampoos with a fruity or floral scent.
  • Wear white, beige and other light colours. Avoid wearing bright coloured clothing, especially floral prints.
  • When outdoors, check inside the can or glass before drinking and make sure there are no stinging insects inside.
  • Tightly cover food containers and trash cans.
  • Wear shoes when walking outside.
  • When driving, keep your windows rolled up.
  • Have hives and nests near your home removed by a professional.
  • Stay calm and slowly walk away if an insect is near you.
For some people, insect sting allergy can be cured with immunotherapy. This is an allergy desensitizing process where an allergist gradually administers stronger and stronger doses of insect venom over a period of time.


Latex is a milky fluid that comes from the rubber tree. If you are allergic to latex you will react to the proteins found in natural rubber latex. A reaction can occur by coming into contact with latex products or by inhaling airborne latex particles.

Latex allergy is common in people who are exposed to latex often, such as those employed in health care or the rubber industry. Children with spina bifida and other congenital diseases who need multiple surgeries often develop latex allergies. Some people may also react to foods that cross-react with latex such as banana, avocado, chestnut, and kiwi.

The best way to prevent an allergic reaction is to avoid latex. Follow these steps to keep yourself safe:
  • Tell your doctors, dentists and nurses about your allergy.
  • Talk to your children's teachers, child care workers, camp personnel, baby sitters and anyone else who may be responsible for their care.
  • If you must wear gloves, choose gloves made without latex.
  • Carry non-latex gloves so that you have them in case of emergency.
  • Stay away from areas of your workplace where people might be wearing latex gloves.
  • Avoid latex bandages and carry a few non-latex bandages with your auto-injector.
  • Wear a MedicAlert® bracelet so that people will know about your allergy if you are in an accident.


Exercise-induced anaphylaxis (EIA) is not common. For some people, exercise alone can cause a reaction. The reaction usually happens within 45 minutes to an hour of starting to exercise. These reactions commonly involve itching, large hives and suddenly feeling very tired. Generally the symptoms go away when the person stops exercising.

Some exercise-induced anaphylaxis is caused by eating a certain food within a few hours of exercising. The food alone might not cause a reaction, but together with exercise, it does. Foods that commonly cause a reaction are wheat, nuts and shellfish. An allergist can help diagnose food-dependent exercise-induced anaphylaxis (FDEIA). If you have this allergy you should avoid the foods that cause a reaction on days when you will be exercising.

Most allergists tell people with this condition not to give up on exercise. They recommend being careful to exercise with a friend and always have an auto-injector with you.

Unknown (idiopathic)

Idiopathic anaphylaxis is a condition in which anaphylaxis occurs and there is no known trigger. It is difficult to diagnose and is done by eliminating all other possibilities. You doctor should take a thorough history and do a physical exam. They should also do skin prick testing, RAST and other lab tests to rule out common allergens and other diseases before diagnosing idiopathic anaphylaxis.

Steroids seem to be helpful in treating idiopathic anaphylaxis but individual treatment will depend on the frequency and severity of the reactions.