Food Allergies vs. Food Intolerances: Knowing the Difference

Food allergies and food intolerances both cause unpleasant symptoms after eating, but they involve fundamentally different biological mechanisms. Understanding the distinction is important for safety and management. A food allergy involves the immune system. When someone with a food allergy eats the trigger food, their immune system overreacts, producing IgE antibodies. This can cause symptoms ranging from hives, swelling, and vomiting to life-threatening anaphylaxis. Canada’s most common food allergens include peanuts, tree nuts, milk, eggs, wheat, soy, fish, shellfish, sesame, and mustard. A food intolerance does not involve the immune system. It is typically a digestive issue - for example, lactose intolerance occurs when the body lacks the enzyme to digest lactose. Symptoms include bloating, gas, diarrhea, and stomach cramps. While uncomfortable, food intolerances are not life-threatening. Key differences: food allergies can cause anaphylaxis (food intolerances cannot), even tiny amounts can trigger allergic reactions, while intolerances are usually dose-dependent, and food allergy testing involves skin prick tests or blood tests (IgE), while intolerances are diagnosed through elimination diets. If you suspect a food allergy, consult your physician for proper testing. Anaphylaxis requires an epinephrine auto-injector (EpiPen). This article is for informational purposes only.

This article is for informational purposes only and does not constitute medical advice. Content reviewed by licensed Canadian physicians. Last updated August 2026.