It is estimated that almost one in ten Canadians suffer from food allergies and this number is rising. For example, in the past, only about 7% of people said they had a food allergy. In 2016, that number grew to 9%.

Based on these numbers, there is a very good chance that you or someone you know suffers from food allergies. For a better understanding of food allergies, let's review the basics.

What are food allergies?

A food allergy occurs when the body’s immune system sees certain food proteins as harmful and reacts by triggering an allergic reaction.

You might be wondering what is the immune system. The immune system is the part of the body that protects us from any infection, like viruses, bacteria and other foreign particles which are outside the body.

As such, you could say that if your immune system perceives proteins in certain foods as harmful and triggers an allergic reaction, you are allergic to those foods.

Food allergies can develop at any age. However, food allergies are more common during childhood and infancy.

Type of Food Allergies

Food allergies can be of two broad types:

  1. Immunoglobulin E (IgE) mediated food allergy
    This term is used when one's immune system makes antibodies known as IgE antibodies to cause symptoms after sudden exposure to the food allergen. It is the most common form of food allergy and this type of food allergy can trigger life-threatening reactions known as anaphylaxis.
IgE antibodies are protein molecules. You can think of these as Y-shaped small antennae. These lie on the surface of allergy cells called mast cells and basophils and detect a specific food protein , for example, cow's milk protein.When these IgE antibodies come in contact with the food protein you are allergic to, they signal the allergy cells to release chemicals such as histamine which then produce allergic symptoms.
Histamine is a chemical compound that is produced by the body and released as part of an allergic reaction. Histamine causes inflammation and allergic symptoms such as sneezing, watery eyes, and skin rashes. It also causes stomach problems such as nausea and diarrhea.

2. Non-IgE mediated food allergy
This term is used when one's immune system reacts to sudden exposure of the food allergen to cause symptoms but does not involve IgE antibodies during the process. This type of food allergy is also known as "cell-mediated" food allergy.

The two most common types of non-IgE-mediated food allergy include food protein-induced enterocolitis syndrome (FPIES) and food protein-induced allergic proctocolitis (FPIAP). We will cover the details of these two in a separate article.

Food allergies versus Food Intolerances

Food allergies are often confused with food intolerances. However, they are not the same. Unlike food allergies, food intolerances are not caused by the immune system and are generally not life-threatening.

Instead, intolerances are caused by small molecules that are found in food that are not readily digested by the body. This causes the symptoms such as indigestion, gas, bloating or diarrhea. For example, lactose intolerance happens when one's body cannot digest lactose due to insufficient production of an enzyme called lactase.

Lactose is a kind of sugar present in cow's milk.


In conclusion, food allergies can be considered to be a hypersensitivity reaction of the body's immunologic system. The type of food allergies include Immunoglobulin E (IgE) mediated or Non-IgE mediated food allergies. Food allergies are not food intolerances.

In the next few articles, we will cover food allergies symptoms and anaphylaxis, common food allergies and food allergy testing.


  • Clarke AE, Elliott S, St-Pierre Y, Soller L, La Vieille S, Ben-Shoshan M. Temporal Trends in Prevalence of Food Allergy in Canada. J Allergy Clin Immunol Pract; April 2020; 8(4): 1428-30
  • L. Soller, M. Ben-Shoshan, D.W. Harrington, M. Knoll, J. Fragapane, L. Joseph, et al. Prevalence and predictors of food allergy in Canada: a focus on vulnerable populations. J Allergy Clin Immunol Pract; March 2015; 3(2): 42-49.
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