Are food sensitivity tests accurate? Here's the truth from an immunologist

The at-home testing industry is booming. From Covid tests to DNA tests, “consumer-initiated lab testing” may be worth as much as $2 billion by 2025, according to Quest Diagnostics. At-home tests make it easier than ever to understand your health right from your home. And for those with chronic gut issues — everything from bloating and gas to heartburn and indigestion — food sensitivity tests claim to help you finally pinpoint the source of your digestive distress and squash it for good by avoiding those trigger foods.

The tests aren’t cheap, either, with some costing consumers upwards of $300. But what, exactly, are these tests looking for, and how accurate are the results? Before shelling out your hard-earned cash for a food sensitivity testing kit, here's what you should know.

The difference between food allergies, food intolerance, and food sensitivities

To understand whether or not food sensitivity testing kits can tell you anything worthwhile, it’s important to understand what they claim to measure and how that differs from food allergies or food intolerance.

When you’re allergic to a food, your body generates an immune response when it comes into contact with it. Andrea Love is an immunologist and microbiologist who works as an immunology consultant for the biotech industry and co-hosts the Unbiased Science podcast. She tells Inverse that “food allergies are immune-related responses where the immune system recognizes a molecule in a food item as ‘foreign’ and mounts an inflammatory response.” When that happens, “our immune system recognizes normally benign antigens, called allergens, as harmful.” That prompts the immune system to produce antibodies called immunoglobin E (IgE), which initiates the production of inflammatory chemicals like histamine, which can progress to anaphylaxis if severe enough and can be fatal.

Symptoms of food allergies include:

• Swelling/itching of lips and mouth
• Tightness in the throat or hoarse voice
• Nausea and vomiting
• Diarrhea and abdominal cramps
• Hives
• Swelling of the skin
• Wheezing or difficulty breathing, which is often an indicator of anaphylaxis

In less common instances, there are non-IgE-mediated allergic reactions: These are non-immediate, occurring hours to days after consumption, and typically result in gastrointestinal symptoms. Celiac disease—the inability to digest gluten— falls into this category.

Food intolerances, on the other hand, “occur in the gastrointestinal tract and are typically due to not being able to properly digest a particular food properly,” Love says. One example is lactose intolerance, where “individuals do not produce sufficient levels of the enzyme lactase required to digest the lactose sugars in dairy products.”

According to the Mayo Clinic, food intolerance is more common than food allergies and only affects the digestive system. In addition to lacking enzymes, some food intolerances are caused by Irritable Bowel Syndrome because the gut may be hyper-reactive to certain foods. Others may not be able to tolerate food additives like sulfites which are commonly found in canned foods and wine.

Food sensitivities, on the other hand, “are not a clinically recognized condition,” Love says. “They can be used to mean anything. Sometimes, this term is incorrectly used instead of food intolerance, such as sulfate and histamine sensitivity. Other times, it’s used as a catchphrase that includes both food allergies and intolerances.”

How do food sensitivity tests purportedly work?

Instead of focusing on IgE, as one would with testing for an allergy, food sensitivity tests focus on immunoglobin G (IgG). Immunoglobulin G is the most common antibody found in blood circulation.

“IgG antibodies are considered antibodies of ‘tolerance’ – their presence simply means you’ve repeatedly been exposed to a molecule in question. In fact, IgG levels may directly correlate with how frequently you consume a given food and has nothing to do with being allergic or ‘sensitive’ to a food product, Love says. “Unfortunately, using these tests leads many to believe they should be avoiding foods that they test ‘positive’ for when these tests are simply saying a person has recently encountered those items.”

The lack of evidence supporting IgG tests is why the American Academy of Allergy, Asthma, and Immunology and the Canadian Society of Allergy and Clinical Immunology (CSACI) advise against using such tests.

“These tests are all marketing and no science,” Love says. “[They are] not accurate and can promote disordered eating and exacerbate nutritional issues.”

How food allergies and intolerance should be diagnosed

If you’re concerned you might have a food allergy or intolerance, “Go to a trained allergist and immunologist,” Love says. “Some tests can be useful, but clinical history is very important to determine whether some of these types of testing performed by allergists (such as skin pricks and blood IgE testing) are false positives. Direct-to-consumer tests are not reliable, are not validated, and cannot be used to diagnose yourself with a medical condition.”

If you find that a particular food doesn’t agree with you, but you don’t test positive for an allergy or intolerance, “there’s no reason to force yourself to eat it. There is a lot we know and a lot we don’t know about the complex body systems, including the immune system, the gastrointestinal system, and even our microbiome.”

Crucially, Love says, if you want to figure out what those foods are, you should always do so under the supervision of a physician.

“There is so much misinformation out there about the immune system and foods, both intentional and unintentional,” Love says. “Consult with your clinical team before making any dramatic changes to your lifestyle habits, especially rigid elimination diets, which these direct-to-consumers tests often recommend based on your test results.”