Food Allergy or Food Intolerance? How to Tell Them Apart

What is a food allergy?

A food allergy is an abnormal immune system response to a specific food. For various reasons, the immune system mistakenly identifies the food in question as harmful, and it triggers a defense reaction by producing massive amounts of chemical mediators, including histamine, to destroy it. Histamine is the primary cause of typical allergy symptoms:

- Skin: redness, itchiness, rash (hives), swollen lips or eyelids

- Respiratory tract: nasal congestion, sneezing, hoarseness, cough, trouble breathing, wheezing

- Digestive system: itchy or swollen mouth, trouble swallowing, nausea, repeated vomiting, stomach pain, diarrhea

- Cardiovascular system: weakness, drop in blood pressure

Allergy symptoms usually appear soon after the food is ingested, i.e., within minutes or hours. They can affect various systems and their severity can vary from one person to another, and sometimes from one reaction to another in the same person.

When symptoms are severe and affect more than two systems, it is referred to as anaphylaxis. Anaphylaxis is a medical emergency that requires an injection of epinephrine and medical supervision. When left untreated, anaphylaxis can be fatal. Even if symptoms are mild, it is important to monitor the person’s state, as the situation can worsen rapidly.

While any food can trigger an allergic reaction, nine food groups are responsible for 90% of allergic reactions:

• Eggs
• Cow’s milk
• Peanuts
• Fish and seafood, e.g., shrimp, crab, lobster, mussels
• Soy
• Nuts, e.g., walnuts, almonds, cashews, hazelnuts
• Mustard
• Sesame
• Wheat

The best way to avoid an allergic reaction is to avoid consuming the food you are allergic to. Learn to read food labels so you can steer clear of known allergens. In some cases, you should also avoid substances that are chemically similar and that can cause allergic cross-reactivity.

People with food allergies should always have an epinephrine auto-injector close at hand.

What is a food intolerance?

According to studies, 7% to 8% of Canadians report suffering from a food allergy, but the actual number of cases confirmed by a physician is lower (3% to 4%). Many people mistakenly believe they have a food allergy when in fact they are actually intolerant to one or more specific foods.

Food intolerances trigger an unpleasant reaction to a particular food. The reaction, however, unlike with allergies, does not involve the immune system. In most cases, the intolerance is caused when the body has trouble digesting a food, or one of its ingredients.

People with food allergies can experience a severe reaction even when only trace amounts of the allergen are present in the food. By comparison, people with a food intolerance can sometimes eat small amounts of the food in question without experiencing any discomfort. While they may be unpleasant, food intolerance symptoms are not life threatening, and since they are rarely specific, it can be hard to pin down the culprit.

Food intolerances are sometimes caused by the absence of a digestive enzyme that normally helps break down food completely. The most common is lactose intolerance.

People who are lactose-intolerant produce insufficient or no lactase, the enzyme that allows the body to digest lactose, the natural occurring sugar in milk. As a result, the lactose stays in the intestines, causing gastrointestinal symptoms that vary in severity depending on the person’s natural ability to produce lactase.

People who suffer from lactose intolerance experience varying degrees of symptoms, including gas and bloating, diarrhea, nausea, and vomiting when they consume milk or foods that contain milk. In most cases, if they take lactase tablets before eating any foods that contain milk, they will usually be able to limit such digestive symptoms. Dairy products such as yogurt and cheese contain less lactose than milk, and are generally easier to digest for people who are lactose intolerant. Lactose-free dairy products are also available.

Sensitivity to a food additive is also another possible cause of food intolerance. Some additives, including artificial color, sulfites, and monosodium glutamate (MSG) can cause symptoms that may or may not be specific or severe, including headache, nausea, chest pain, trouble breathing, skin rashes, generalized malaise, and fatigue.

Irritable bowel syndrome (IBS) is another form of food intolerance. It is believed to be caused by a nervous system disorder that creates hypersensitivity of the digestive system to certain foods. People with IBS tend to experience abdominal pain, constipation, or diarrhea when they eat certain foods. Taking probiotics can help reduce symptoms. A significant proportion of people with IBS who switch to a diet called low-FODMAP report an improvement in their symptoms. The low-FODMAP diet is low in foods containing certain carbohydrates that ferment in the intestines However, it is recommended you consult a nutritionist before adopting this type of diet, to avoid developing any nutritional deficiencies.

Gluten intolerance and celiac disease

People who are gluten intolerant experience a range of different symptoms after eating foods that contain gluten, including gas and bloating, and fatigue.

Celiac disease is not a food allergy. Rather, it is an auto-immune disease triggered by the presence of gluten in one’s diet. When the person eats foods containing gluten, it causes inflammation of and damage to the small intestine, which can impair their body’s ability to absorb nutrients that are essential to their health. People with celiac disease must avoid eating any foods that contain gluten, as even a very small amount can cause inflammation and symptoms.

While symptoms of celiac disease vary from one person to another, they usually include vomiting, abdominal pain, diarrhea, and involuntary weight loss. Unlike food allergies, to wheat, for example, these symptoms do not develop into an anaphylactic reaction.

What to do if you think you might have a food allergy or intolerance?

Severe food allergies usually appear starting in childhood. It is more unusual for them to appear in adults. Food intolerances, on the other hand, can develop over time and appear later in life. If you often experience significant digestive symptoms that impede your quality of life, it may be worth investigating whether you have a food intolerance or allergy.

Try keeping a food diary: Write down everything you eat and any unusual symptoms you feel. You may be able to draw a link between a specific food and the onset of such symptoms.

Consider making an appointment to see a nutritionist, who can help you adjust your diet so you don’t develop any nutritional deficiencies. Nutritionists are professionals who can also show you how to read and understand nutrition value labels on foods at the grocery store so you can identify the substances you should stay away from.

Discuss your concerns with your health professional. In some cases, they may prescribe certain tests or refer you to an allergy specialist. This is essential before an allergy diagnosis can be made.

Food Allergy Canada is an excellent resource for those living with food allergies. Feel free to consult their website for information on how to manage your new reality and eat without fear.

If you have questions about treatment for food allergies or medications that can alleviate food intolerance symptoms, consult your pharmacist. They can provide advice or direct you to another health professional, as needed.