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Food Allergies & Intolerances

Food Allergies & Intolerances

What's the difference between a food allergy and food intolerance? What can you do if you think you are sensitive to certain foods? Learning what foods you need to avoid is important for anyone with serious food allergies.

What is a food allergy?

A food allergy is an immune system response to a substance in food, usually a protein. The substance that you are allergic to is called an allergen. When an allergen is eaten it can cause an allergic reaction in the respiratory or digestive systems, or the skin. Typical symptoms are wheezing or breathing difficulties, vomiting, diarrhea, skin rashes or hives.

The most common food allergens include:

  • Peanuts
  • Tree Nuts (e.g., walnuts, almonds, hazelnuts, cashews)
  • Milk
  • Eggs
  • Fish
  • Shellfish (e.g., shrimp, crab, lobster, mussels)
  • Soy
  • Sesame Seeds
  • Wheat
  • Mustard

What is a food intolerance?

A food intolerance is an unpleasant reaction to a food that does not involve the immune system (which is different than an allergic reaction).

For example, lactose intolerance is what happens when the body cannot breakdown lactose, a natural sugar found in milk. This is different than a milk allergy, which is caused by an immune response to the protein in cow's milk.

Should you avoid milk if you have lactose intolerance?

That depends. Some people who have lactose intolerance may be able to tolerate a small amount of milk taken with meals. Start with ½ cup (125 mL) of milk at a time to see how much you are comfortable drinking.

You can also drink lactose-reduced or lactose-free milk, or use the commercially available drops or tablets that help break down lactose in foods.

If you cannot tolerate milk, you may still be able tolerate milk products that have very little lactose like yogurt or hard cheeses.

However, if you are very sensitive to lactose you may need to avoid all foods containing lactose. Your doctor can test you for lactose intolerance.

If you’d like a handout on foods that contain lactose, call 1-877-510-510-2 or send an email.

What is an anaphylactic reaction?

Anaphylaxis is the most severe type of allergic reaction. It is sudden, severe and potentially life-threatening. An anaphylactic reaction can be caused by a food allergy, insect stings or medications.

Almost any food can cause an anaphylactic reaction but the most common are peanuts, tree nuts, shellfish, fish, cow's milk, eggs, sesame, and soy. People with asthma and food allergies are at greater risk of having an anaphylactic reaction to foods.

Symptoms of an anaphylactic reaction:

  • Difficulty talking
  • Difficulty swallowing
  • Difficulty breathing
  • Drop in blood pressure
  • Rapid heartbeat
  • Unconsciousness

What should you do if you suspect a food allergy or intolerance?

Discuss your concerns with your family doctor. He or she can refer you for tests or to an allergy specialist. Getting a proper diagnosis is important as some food allergies can be severe and life threatening.

The most important action for people with food allergies is to avoid foods that cause a reaction. Reading food labels and checking with food manufacturers and restaurants is very important to know which foods to avoid.

Individuals who are at high risk for anaphylactic reactions must be especially careful to avoid allergy causing foods and should carry an epinephrine auto injector (i.e. Epipen® or Twinject) with them at all times.

If you have a food intolerance, you may still be able to eat small amounts of that food. For example, if you have a lactose intolerance you may not be able to drink milk but can eat yogurt. Everybody with an intolerance reacts differently and you will have to decide what works for you.

Can a child outgrow an allergy?

Some children 'outgrow' their food allergy to milk, soy and egg within a few years. Allergies to peanuts, tree nuts, fish and shellfish are more likely to last to adulthood. About 20% of children can outgrow their peanut allergy by school age. 

Speak to your doctor for more information to know whether your child has outgrown an allergy.

You may also be interested in:

Peanut Allergies FAQs

Managing Milk Allergies

Facts about Wheat Allergies

For more information:

Food Allergy Canada

Asthma Allergy Information Association

Last Update – July 12, 2017

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If you have questions about what you've read here, or other questions about food, nutrition or healthy eating, click to email our Registered Dietitians or call 1-877-510-5102.