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Food Sensitivity Tests

What Are They, When They Are Used, How They Are Performed, and More

Author:Lily Guo

Editors:Alyssa Haag,Ian Mannarino, MD,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:Sadia Zaman, MBBS, BSc


What are 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.

There is currently no consensus in the medical literature on the definition of food sensitivity, and physicians or dietitians are more likely to use the term food intolerance. Lactose intolerance, a common form of food sensitivity, is characterized by the inability to digest milk or dairy products, resulting in digestive issues like gas and bloating. This occurs when the individual doesn’t make enough lactase, which is the enzyme used to break down lactose into the simple sugars glucose and galactose. It is important to note that none of the current tests for food sensitivity currently on the market have been evaluated by the Food and Drug Administration (FDA), nor have they been validated through rigorous, blinded clinical trials. 

Woman with rash secondary to food sensitivity.

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

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. 

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Why are food sensitivity tests used?

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. 

It is important to note that besides breath tests that can be used to diagnose certain intolerances (e.g., lactose), there are no validated tests for food intolerances or sensitivities. Some studies suggest that the presence of antibodies may not be an accurate or reliable marker of a food sensitivity, especially because many other antibodies and cell-mediated reactions may be involved in food sensitivities. Current at home food sensitivity tests cannot diagnose food sensitivity and may even lead to misdiagnosis of possible underlying conditions (e.g., Celiac disease). Overinterpreting or misinterpreting test results can lead to unnecessary food restrictions, increased stress and anxiety surrounding food, fear of foods, as well as overall poor nutrition and wellness. In some cases, changing one’s diet drastically may worsen gastrointestinal symptoms. If an individual is experiencing stomach or bowel issues, it may be important to speak to a clinician before making drastic nutritional changes. 

How are food sensitivity tests done?

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.

Laboratories commonly use an immunoglobulin G antibody assay to test if an individual has food sensitivities. An IgG antibody is a memory antibody that determines exposure to a food. Companies claim that if foods that elicit a high IgG response are removed from one’s diet, gastrointestinal symptoms will likely improve. However, some research shows that higher levels of IgG subclass four are associated with better tolerance to foods. Other companies use blood samples to measure stimulation of leukocytes including monocytes, lymphocytes, eosinophils, basophils and neutrophils. Monitoring all leukocytes allows for assessment of all chemical sensitivities regardless of the pathway (e.g., immunologic, toxic, pharmacologic), since cells may release free radicals and inflammatory mediators without antibody involvement. Lastly, other laboratories determine sensitivity to foods by measuring “bioresonance” of the hair, defined as the energy wavelengths coming from the body

How do food sensitivities affect the body?

Food sensitivities are believed to be caused by an immune reaction primarily driven by the IgG, IgA, IgM, and other cell mediated reactions. IgG-specific antibody-mediated reactions are a body's natural and normal defensive reactions to infiltrating food antigens, which are absorbed into the bloodstream in small quantities. After a meal, food antigens form a complex with antibodies and specific IgG’s circulating in the serum. In healthy individuals, these complexes are easily removed in the reticuloendothelial system (i.e., a system where tissue macrophages remove foreign material from the lymph and blood). In the presence of excess food antigen or antibodies, immune complexes are deposited in the blood vessels of the skin, kidneys, and joints. IgG’s involved in this reaction may initiate adverse food reactions and contribute to chronic intestinal inflammation. 

What are the most important facts to know about food sensitivity tests?

Food sensitivity tests refer to laboratory tests that measure the body’s immune response to certain foods. They are designed to identify which foods in one’s diet are leading to food sensitivity and adverse gastrointestinal symptoms, such as abdominal bloating, cramping, diarrhea, and heartburn. Common foods tested include dairy, meats, grains, and nuts. Food sensitivity tests are used to supplement food elimination testing which can be used to diagnose food sensitivities. Multiple tests are marketed to diagnose food intolerances, however, it may be recommended to seek help from a health care provider if digestive symptoms are interfering with one’s daily life. 

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Related links

Food allergy
Food allergies and EpiPens: Information for patients and families (The Primary School)
Antibody classes

Resources for research and reference

Geiselman, J. F. (2019). The Clinical Use of IgG Food Sensitivity Testing with Migraine Headache Patients: a Literature Review. Current Pain and Headache Reports, 23(11): 79. DOI:10.1007/s11916-019-0819-4

Gocki, J.,  & Bartuzi, Z. (2016). Role of immunoglobulin G antibodies in diagnosis of food allergy. Postepy Dermatologii i Alergologii, 33(4): 253-6. DOI: 10.5114/ada.2016.61600. 

Ho, M. H., Wong, W. H., & Chang, C. (2014). Clinical spectrum of food allergies: a comprehensive review. Clinical reviews in allergy & immunology, 46(3): 225–240. DOI: 10.1007/s12016-012-8339-6

Manuyakorn, W., & Tanpowpong, P. (2019). Cow milk protein allergy and other common food allergies and intolerances. Paediatrics and international child health, 39(1): 32–40. DOI: 10.1080/20469047.2018.1490099

Mullin, G. E., Swift, K. M., Lipski, L., Turnbull, L. K., & Rampertab, S. D. (2010). Testing for food reactions: the good, the bad, and the ugly. Nutrition in Clinical Practice, 25(2): 192-198. DOI: 10.1177/0884533610362696

Smith, E., Foxx-Orenstein, A., Marks, L. A., & Agrwal N. (2020). Food Sensitivity Testing and Elimination Diets in the Management of Irritable Bowel Syndrome. Journal of the American Osteopathic Association, 120(1): 19-23. DOI: 10.7556/jaoa.2020.008

Weiss, C. (2022, April 13). Mayo Foundation for Medical Education and Research. Mayo Clinic Q and A: Testing for food allergies and sensitivities. In Mayo Clinic. Retrieved September 18, 2022, from https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-testing-for-food-allergies-and-sensitivities/