Food Sensitivity Tests

Food sensitivity tests, also known as food intolerance tests, refer to laboratory tests that can measure the body’s immune response to certain foods. Food sensitivity occurs when immunoglobulin A (IgA), immunoglobulin G (IgG), white blood cells, and other immune system molecules react to certain food(s) in one’s diet. In those with food sensitivities, the immune reaction triggers gastrointestinal upset, problems with digestion, and gut inflammation. Symptoms include abdominal pain, bloating, indigestion, heartburn, and diarrhea. There may be additional adverse symptoms such as headache, joint pain, fatigue, difficulty sleeping, rashes, and skin changes. 

The types of foods that trigger food sensitivity vary from individual to individual. Common foods that may cause sensitivity include dairy products (e.g., cheddar cheese, cottage cheese, cow's milk, mozzarella cheese, yogurt); egg white and egg yolk; grains (e.g., barley, bran, brown rice, gluten); fruits (e.g., apple, avocado, banana); meat (e.g., beef, chicken, lamb); and more.

A food sensitivity differs from a food allergy, as food sensitivities are linked to an increase in IgG antibodies, IgA and IgM antibodies, whereas food allergies typically elicit IgE reactivity. Food sensitivities are a non-life-threatening condition with symptoms occurring hours or even days after eating a certain food, and often resolve when the offending food is avoided. Food sensitivity can be diagnosed at any age. 

In contrast, the mechanism of food allergies involves the IgE antibody binding to a mast cell. This causes the mast cell to release histamine, causing itching, hives, rash, vomiting, and swelling of the tongue, lips, and/or throat. In severe cases, an anaphylactic reaction, where breathing becomes impaired, can occur. Other symptoms include runny nose, sneezing, congestion, and tingling of the skin. Symptoms may overlap with those of food sensitivity and include abdominal pain, nausea, and diarrhea. In most situations, a food allergy will cause a more immediate reaction, within a few minutes of consuming even a small amount of the offending food. Food allergies are more commonly diagnosed in infants and young children, however, adults can also develop allergic reactions to food. Approximately 32 million people in the U.S. have food allergies, with the most common triggers including milk and other dairy products; eggs; peanuts; fish; crustacean shellfish; wheat; tree nuts; soy; and sesame. These food items account for approximately 90% of food allergies. 

Food allergy testing may be performed via a skin test, where a small amount of an allergen is placed on the skin, typically on the back or forearm. The skin is then gently scratched to introduce the allergen into the skin. If there is a possible allergy, a red induration will appear within 10-15 minutes, with the size and redness of the bump indicating severity of the allergy. In addition to a skin test, some may undergo immunoglobulin E antibody food-specific blood tests. Food allergy tests are typically performed by a qualified healthcare professional, such as a trained allergist. 

Food sensitivity tests are used to help reduce the intake of certain foods in the diet that may be contributing to the individual’s gastrointestinal symptoms. Food sensitivity tests are not diagnostic tests, but are primarily used to help guide what types of food an individual may prioritize within an elimination diet. An elimination diet is the current gold standard for diagnosing a food sensitivity and is performed by a licensed healthcare professional such as a gastroenterologist, allergist, dietitian, or nutritionist. Elimination diets involve removing foods from the diet that are suspected to cause symptoms of sensitivity, or foods that commonly cause symptoms in the general population (e.g., nuts, dairy, seafood). The foods are eliminated for 2-3 weeks then  re-introduced one at a time, over 2-3 days. The clinician will continuously monitor and assess for symptoms associated with re-introduction of specific foods including bloating, stomach pain or cramps, and changes in bowel habits. 

The food sensitivity test can be used, alongside other testing methods and treatments recommended by a clinician or dietitian, to help make adjustments to one’s diet and minimize gastrointestinal symptoms. 

Food sensitivity tests can be done in providers’ offices, however, they are also available as at-home tests, which can be purchased online or over-the-counter at drug stores. Depending on the test type, at-home lab tests require a finger prick blood sample or a few hairs that are collected and mailed in. Within days or weeks, the individual will typically receive digital results, including a list of foods that may be causing problems.