Adverse reactions to food can be broken down into three categories: Allergies, intolerances, and sensitivities.

Food Allergies
True food allergies are immune reactions to food. These reactions begin to cause symptoms immediately after a trigger food is eaten.

Symptoms can range from mild to severe and may include a rash, swollen or itchy tongue, runny nose, hives, abdominal pain, vomiting, trouble breathing, coughing, wheezing, or a closed airway.

Common food allergens: peanuts, tree nuts, wheat, soy, milk, eggs, fish, shellfish, and sesame. Many other foods can also cause allergic reactions.

Food Intolerances
Food intolerances are non-immune reactions to specific food components (e.g., lactose, histamine, alcohol, etc.) that occur when a person lacks the digestive enzyme or nutrient responsible for breaking down those components. Intolerances can cause flushing, cold or flu-like symptoms, inflammation, and general discomfort.

Typical food intolerances: dairy products, sulphites, histamines, lectins, preservatives, artificial colours, fillers, flavourings, chocolate, citrus fruits, and acidic foods.

Food Sensitivities
Food sensitivities can cause reactions that are delayed by hours or even days. These food reactions are usually caused by an imbalance in the gastrointestinal system that affects the immune system. One such imbalance is increased intestinal permeability or “leaky gut.”

Symptoms of food sensitivities differ from person to person and can depend on the type of food eaten. Some symptoms are migraines, headaches, dizziness, difficulty sleeping, mood swings, depression, anxiety, unintentional weight loss or gain, dark under-eye circles, asthma, irregular heartbeat, irritable bowels, bloating, wheezing, runny nose, sinus problems, ear infections, food cravings, muscle or joint pain, indigestion, nausea, vomiting, bladder control issues, fatigue, hyperactivity, hives, rashes, dry skin, excessive sweating, and acne.

Common food sensitivities: cow’s milk (and other dairy products), eggs,
gluten (from wheat, rye, and barley), soy, shellfish, and tree nuts. Many other foods and ingredients can also cause sensitivity reactions.

Identifying Adverse Reactions to Food
If you suffer from a food allergy, you are likely aware of the allergy and already avoid trigger foods. However, if you or your healthcare practitioner suspects that you have a food intolerance or sensitivity, the best way to identify the foods that cause negative symptoms is to eliminate those foods from your diet for a certain period and then reintroduce those foods one by one, paying close attention to your body’s reaction. Some laboratory tests can help assess for food sensitivities and intolerances, although an elimination diet is likely the most accurate way to proceed.