What is the difference between a food allergy and a food intolerance?

November 9, 2015 Lisa Cantkier


I am often asked, “What is the difference between a food allergy and a food intolerance?”

The answer can sound confusing, especially when it comes to celiac disease (CD) which doesn’t truly fit into just one category because CD is an autoimmune disease whereby the body’s immune system reacts to gluten. In CD there is both an intolerance to gluten and an autoimmune response.

I hope these definitions help explain the difference between allergies and intolerances for you (I underlined some of the important parts). Whether you or a loved one have an allergy or an intolerance, both should be taken very seriously and the food(s) in question should be completely avoided at all times.

According to Health Canada:

Food allergies are sensitivities caused by a reaction of the body’s immune system to specific proteins in a food. According to a recent publication1, approximately 7% of Canadians self-report a food allergy. However, fewer are likely to have a physician-diagnosed food allergy, which are estimated at prevalence levels up to 5-6% for young children and 3-4% for adults in westernized countries2 3 4 5.

In allergic individuals, a food protein is mistakenly identified by the immune system as being harmful. The first time the individual is exposed to such a protein, the body’s immune system responds by creating antibodies called immunoglobulin E (IgE). When the individual is exposed again to the same food protein, IgE antibodies and chemicals such as histamine are released. Histamine is a powerful chemical that can cause a reaction in the respiratory system, gastrointestinal tract, skin or cardiovascular system. In the most extreme cases, food allergies can be fatal (anaphylaxis). Although any food can provoke an immune response in allergic individuals, a few foods are responsible for the majority of food allergies.

A food intolerance is a food sensitivity that does not involve the individual’s immune system. Unlike food allergies, or chemical sensitivities, where a small amount of food can cause a reaction, it generally takes a more normal sized portion to produce symptoms of food intolerance. While the symptoms of food intolerance vary and can be mistaken for those of a food allergy, food intolerances are more likely to originate in the gastrointestinal system and are usually caused by an inability to digest or absorb certain foods, or components of those foods.

For example, intolerance to dairy products is one of the most common food intolerances. Known as lactose intolerance, it occurs in people who lack an enzyme called lactase, which is needed to digest lactose (a sugar in milk.) Symptoms of lactose intolerance may include abdominal pain and bloating, diarrhoea and flatulence.

A food sensitivity is an adverse reaction to a food that other people can safely eat, and includes food allergies, food intolerances, and chemical sensitivities.

1. Overall Prevalence of Self-reported Food Allergy in Canada, L. Soller et al, Journal of Allergy and Clinical Immunology (2012). doi: 10.1016/j.jaci.2012.06.029

2. Prevalence and cumulative incidence of food hypersensitivity in the first 3 years of life. C Venter et al, Allergy 2008: 63: 354-359.
3. Maternally reported food allergies and other food-related health problems in infants: Characteristics and associated factors. S Luccioli et al. Pediatrics, volume 122, sup. 2, S105-S112, October 2008.
4. Prevalence of adverse reactions to food in Germany – A population study. T Zuberbier et al. Allergy 2004: 59: 338-345.
5. The prevalence of food hypersensitivity in an unselected population of children and adults. M Osterballe et al. Pediatric Allergy and Immunology 2005: 16: 567-573.

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