Food Allergy vs. Food Intolerance

Diet is a key component of a healthy lifestyle. Beyond consuming the recommended daily servings of the necessary food groups, it is important to know which foods, if any, you should avoid. Food allergies and intolerances (or sensitivities) affect many of us, and it is crucial to know the differences.

Food allergy involves an abnormal immune reaction to a non-pathogenic substance. The body reacts as if it were fighting a disease-producing microorganism, which can cause symptoms ranging from discomfort to potentially life-threatening anaphylaxis, and can include abdominal pain, diarrhea, vomiting, hives, swelling of the lips and face, shortness of breath, dizziness, low blood pressure, anxiety, and heart failure. Food allergies can affect as many as 5-6% of young children and 3-4% of adults in Westernized countries. Approximately 7% of Canadians self-report a food allergy.1

Food intolerance is an adverse reaction to food that is likely to originate in the gastrointestinal tract and does not involve the immune system. This umbrella term includes lactose intolerance and non-celiac gluten intolerance along with a broad range of other sensitivities. Symptoms are not life threatening, and are typically limited to digestive symptoms such as diarrhea, bloating, and nausea. Symptoms can appear soon after eating or could take up to two days.2


Allergy History & Facts

Allergies include conditions such as hay fever, atopic dermatitis, and allergic asthma. Common allergens include a variety of foods, pollen, dust, animal dander, insect stings, certain drugs, perfumes and fragrances, and many other substances. Even ubiquitous foods such as lettuce can trigger an allergic reaction. Depending on the severity of a person’s allergy, inhalation, oral consumption, and even touch can trigger a reaction.3

Drug allergies can be very severe. The most common drug allergens include penicillin, sulfa medicines, and non-steroidal anti-inflammatory drugs (NSAIDs). Seek medical attention immediately if you suspect an allergic reaction to a medication.4


Allergy Testing & Treatment

The gold standard for diagnosing allergies involves either skin prick testing or patch testing. Skin prick testing and patch testing are similar in that the tester applies allergens to the skin and then measures the patient’s reaction to determine allergic reaction. Skin prick and patch testing are the least expensive and easiest methods for diagnosing allergies in most people. Immediate results are available after testing is complete. There are also blood tests to diagnose allergies. These are ideal for people who are not able to do skin tests. However, blood tests cost more than skin prick and patch tests and are less sensitive. This means that it is possible for a skin prick or patch test to produce a positive result and a blood test to produce a negative result from the same patient. Unlike skin prick and patch testing, a patient may have to wait seven days or more to receive the results from a blood test.5

The best form of treatment for allergies, especially food allergies, is avoidance. In the event of an allergic reaction, there are a few treatment options available depending on the severity of the reaction. For serious reactions, epinephrine injection, administered by an EpiPen®, is the first step to treat anaphylaxis as the medication quickly reverses the effect of the attack. Give an epinephrine injection, then call 9-1-1 and notify emergency services that someone is having an anaphylactic reaction. Give a second dose of epinephrine five minutes after the first dose if there is no improvement of symptoms. You must seek medical attention at the nearest hospital, even if symptoms improve after the first or second injection.6 Antihistamines and corticosteroids can treat milder symptoms (more common with non-food allergies) of an allergic reaction but not anaphylaxis.7


Food Intolerance Testing: Does it Work?

Reputable food allergy tests are available through physician specialists known as allergists or immunologists, but there are no reliable tests for food intolerances. However, some independent labs have produced their own blood testing systems that they claim can identify food intolerances, which are available at a select number of retail pharmacies or health food stores. However, the medical science community has raised concerns regarding the efficacy of these testing systems, so medical doctors will rarely ask you to go for these, often expensive, tests that produce questionable results.

The Investigations Committee of the Quebec College of Physicians (CMQ) warns against medical professionals recommending these testing systems to their patients. The Committee observes that labs promoting food intolerance testing present non-validated conclusions. They reaffirm the duty of licensed medical professionals to only administer any sort of testing when medically necessary, and that there is a greater need to be critical of data coming from unrecognized sources or from promotional material.8

The Canadian Society of Allergy and Clinical Immunology says, “There is no body of research that supports the use of [these] tests to diagnose adverse reactions to food or to predict future adverse reactions.” They issued their position in support of similar opinions expressed by the American Academy of Allergy, Asthma & Immunology and the European Academy of Allergy and Clinical Immunology regarding the validity of food intolerance testing.9


Final Thoughts

We all want to know what foods we should avoid, especially when it comes to eating something that could result in a potentially life-threatening allergic reaction. Food intolerance testing systems can be expensive and rely on data that the medical science community does not support. Making drastic changes to your diet from these unproven tests could lead to health issues, such as nutritional deficiencies. If you are concerned about dietary choices and potential allergy or sensitivity to a particular food, you should consult your general practitioner for a referral to a qualified specialist.


Five Allergy Facts

  • Viennese pediatrician Clemens von Pirquet introduced the concept of allergy in 1906 after he noticed hypersensitivities in his patients to seemingly innocuous substances including dust, pollen, and certain foods.10

  • The word ‘allergy’ derives from ancient Greek words allos (meaning ‘other or different’) and ergia (meaning ‘energy or reaction’).10

  • Most food allergies are the result of an immune response to certain proteins found in some foods. These proteins trigger the release of anti-inflammatory chemicals including histamine.11

  • Health Canada created a list of priority allergens that require specific labelling guidelines. The current list includes eggs, milk, peanuts, tree nuts, wheat, seafood, sesame, soy, sulphites, and mustard.12

  • Food allergens can appear in unexpected places, including processed foods, vitamins, skin creams, and pet foods. Always read the label and the ingredient list on a food item carefully to ensure that it is free from food allergens that could be harmful to you or your family.13

First published in the Inside Tract® newsletter issue 206 – 2018
1. Government of Canada. Food Allergies and Intolerances page. Available at: Accessed 2018-04-17.
2. Ozdemir O et al. Food intolerance and Eosinophilic Esophagitis in Childhood. Digestive Diseases and Sciences. 2009;54:8-14.
3. McConnell TH. The Nature of Disease: Pathology for the Health Professions. Baltimore, Md: Lippincott Williams & Wilkins; 2007.
4. HealthLink BC. Drug Allergies page. Available at: Accessed 2018-04-17.
5. HealthLink BC. Allergy Tests page. Available at: Accessed 2018-04-17.
6. Food Allergy Canada. Anaphylaxis page. Available at: Accessed 2018-04-17.
7. Sicherer SH. Understanding and Managing Your Child’s Food Allergy. Baltimore, Md: Johns Hopkins Press; 2006.
8. Collège Des Médecins Du Québec. Dosage des IgG «anti-aliments» page. Available at: Accessed 2018-04-17.
9. Carr S et al. CSACI Position statement on the testing of food-specific IgG. Allergy, Asthma & Clinical Immunology. 2012;8:12.
10. Igea JM. The history of the idea of allergy. Allergy. 2013;68:966-973.
11. Mayo Clinic. Food allergy page. Available at: Accessed 2018-04-17.
12. Health Canada. The Canadian Criteria for The Establishment of New Priority Food Allergens page. Available at: Accessed 2018-04-17.
13. Newly Diagnosed Support Centre. Understanding Labels page. Available at: Accessed: 2018-04-17.