Sometimes certain foods can make you feel unwell, regardless of whether they’re healthy.

They may trigger any number of food sensitivity symptoms, such as headaches, digestive issues, joint pain, or skin issues.

It can be tricky to figure out which foods are responsible since food sensitivity reactions may not happen until a few hours or longer after you eat the foods.

To help identify the specific foods that cause adverse reactions, some health professionals may offer food sensitivity tests.

Here’s a closer look at what food sensitivities are and the best tests to identify them.

Three different terms are commonly used for adverse reactions to foods: food allergy, food sensitivity, and food intolerance. However, not everyone defines these terms the same way.

The term “food allergy” is best reserved for potentially life threatening food reactions that involve immunoglobulin E (IgE) antibodies of your immune system. These are true food allergies and can cause dangerous reactions like anaphylaxis (1).

In contrast, food sensitivities and food intolerances generally are not life threatening but may make you feel ill.

Here’s a quick comparison of food allergies, sensitivities, and intolerances (2, 3, 4, 5, 6, 7, 8, 9):

Food allergyFood sensitivityFood intolerance
Immune system involved?yes (IgE antibodies)yes (IgG and other antibodies, white blood cells and other immune system molecules)no (digestive enzyme deficiency, poor absorption of certain carbs)
Examples of foods involvedtop 9 most common: milk, egg, peanut, tree nuts, wheat, soy, fish, crustacean shellfish, and sesamevary from person to person and may include foods you eat oftenfermentable carbs (FODMAPS): milk (lactose), legumes and certain vegetables, fruits, grains, and sweeteners
Onset of symptoms after eating the foodrapid, often within minuteswithin a few hours but may be delayed up to a few dayswithin 30 minutes to 48 hours after eating
Examples of symptomstrouble swallowing or breathing, nausea, vomiting, hives; can result in anaphylaxisheadaches, joint pain, digestive issues, skin issues, an overall feeling of being unwellmost common are digestive issues: bloating, excess gas, gut pain, diarrhea, and constipation
Amount of food needed to cause symptomstinyvaries depending on your degree of sensitivitygenerally worse with larger amounts of problem foods
How it’s testedskin-prick tests or blood tests of IgE levels to specific foodsMany tests are available, but their validity is uncertain.Breath tests may identify fermentable carb intolerances (lactose, fructose).
Age of diagnosiscommonly in infants and young children, but adults can also develop themcan appear at any agevaries, but lactose intolerance is most likely in adults
Prevalence1–2% of adults; less than 10% of childrenuncertain but suspected to be commonup to 20% of the population
Can you get rid of it?Kids may outgrow milk, egg, soy and wheat allergies. Peanut and tree nut allergies tend to continue into adulthood.You may be able to consume a food again without symptoms after avoiding it for several months and addressing any underlying issues.You can minimize symptoms by limiting or avoiding food triggers in the long term. Antibiotic treatment for small intestinal bacterial overgrowth may also help.
Summary

A true food allergy is a potentially life threatening reaction that involves IgE antibodies of your immune system. Food sensitivities involve other antibodies and cells of your immune system, while food intolerances don’t involve your immune system.

If the symptoms are not life threatening and are not caused by a true food allergy, the gold standard for identifying food sensitivities is an elimination diet followed by an oral food challenge.

During a food challenge, you eat the eliminated foods one by one after a period of avoidance to determine your reaction — ideally without you knowing what’s being tested (10).

If you don’t follow an elimination diet before the oral challenge for food sensitivities, your symptoms in response to consuming a food antigen may be hard to detect.

When you stop eating a food that causes an adverse reaction, you may have temporary withdrawal symptoms. You might have to follow an elimination diet for about 2 weeks before these symptoms clear up and you’re ready to start testing foods in an oral challenge.

Following an elimination diet requires dedication and commitment, as well as careful record-keeping. You should know the ingredients of everything you eat, which makes eating out difficult. Keeping a food journal or using a food diary app may help.

The foods you avoid on an elimination diet may vary. Some allergists and immunologists may direct you to eliminate only foods suspected to be a problem, such as those containing dairy, wheat, and soy.

Warning

You should never attempt to reintroduce a food on your own if you have a true allergy. If you suspect you have outgrown a food allergy, talk about the appropriate testing with an allergist.

Others may direct you to eliminate all but a few foods for a short period, such as 2 weeks, and then slowly reintroduce them.

To reduce the guesswork as to which foods may be causing your issues, some practitioners may first give you a food sensitivity test to help guide your elimination diet.

Summary

The gold standard for identifying food sensitivities is an elimination diet followed by a methodical oral food challenge, which involves trying the eliminated foods one by one. Some practitioners use food sensitivity tests to home in on problem foods.

Cell-based tests for food sensitivities began with the cytotoxic test popularized in the 1950s. This test was banned by several states in 1985 due to problems with its accuracy (11).

Since then, immunologists have improved and automated the testing technology. Two available cell-based blood tests for food sensitivities are the Mediator Release Test (MRT) and the Antigen Leukocyte Cellular Antibody Test (ALCAT).

Though some practitioners have reported that they find these tests useful, reputable published studies on the tests are limited (7).

Mediator Release Test (MRT)

The MRT requires a blood sample, typically drawn from a vein in your arm and collected using a kit from the company that has a patent on the test.

If your white blood cells “shrink” when exposed to a food antigen in the MRT test, it causes a change in the solid (white blood cells) to liquid (plasma) ratio of your blood sample. This is measured to determine your reactivity to the food (12).

When your white cells shrink upon exposure to a food antigen, it suggests they’ve released chemical mediators, such as histamine and leukotrienes, that could provoke symptoms in your body.

The diet based on your MRT results is called LEAP (Lifestyle Eating and Performance) and is directed by health practitioners, such as dietitians, who are trained in the test and its interpretation.

A small 2004 study in 10 people found that people with irritable bowel syndrome (IBS) who followed an elimination diet based on MRT results for at least 1 month reported a marked improvement in gut issues, such as diarrhea, as well as overall well-being (13).

However, there was no control group in this study, nor has it been published in full.

New publications on MRT are in progress (14).

However, PubMed, a large database that indexes published medical studies, lists no studies on the MRT.

Antigen Leukocyte Cellular Antibody Test (ALCAT)

The ALCAT is the predecessor of the MRT, but many healthcare practitioners and labs still offer it.

To assess which foods may provoke a reaction for you, it measures changes in the size of your white blood cells (rather than changes in the solid-to-liquid ratio) when exposed to individual food antigens, which may decrease accuracy.

When people with IBS followed a diet based on their ALCAT results for 4 weeks, they reported twice the reduction in certain IBS symptoms, such as abdominal pain and bloating, compared with people following a placebo diet (15).

However, those who followed ALCAT-based diets didn’t rate their IBS relief as being adequate or significantly improving their quality of life during the study (15).

Summary

Cell-based blood tests, including the MRT and ALCAT, assess changes in your white blood cells after exposure to food antigens. Some practitioners report that the tests may be helpful in identifying food sensitivities, but both tests require further study.

Antibody-based food sensitivity tests measure your production of immunoglobulin G (IgG) antibodies to foods. They’re available under various brand names.

This type of test has more published research than other food sensitivity tests, but studies are still limited. These studies suggest that eliminating foods guided by IgG tests may help improve symptoms in people with IBS and migraine (16, 17, 18, 19).

Still, many scientists advise people not to use IgG food sensitivity tests, saying that the presence of IgG antibodies against foods may simply show that you’ve been exposed to the foods or, in some cases, they may be protecting against food allergy reactions (7, 20).

This means these tests may show false positives.

However, other scientists say it’s not normal for someone to have high levels of IgG antibodies against foods.

Another concern is that individual labs that do IgG tests develop their own in-house techniques. Many have varied reproducibility, meaning that if the same blood sample were analyzed twice, it might not show the same results both times (4).

It’s recommended that you use an IgG test only if it evaluates your blood sample twice with each antigen in side-by-side duplicate testing to minimize errors in your results.

Summary

Tests that evaluate levels of IgG antibodies against foods are available under various brand names. They may help identify foods involved in symptoms of conditions such as IBS and migraine. Accuracy is improved if a lab does side-by-side duplicate testing.

Some complementary and alternative medicine practitioners, such as chiropractors, naturopaths, and environmental medicine doctors, may use other tests to check for food sensitivities.

Some of the more common options are muscle response testing, provocation tests, and electrodermal screening.

Muscle response test

Also known as applied kinesiology, the muscle response test involves holding a vial containing a food antigen in one hand while extending your other arm parallel to the floor.

The practitioner then pushes down on your extended arm. If it’s easily pushed down, indicating weakness, you are told that you’re sensitive to the food being tested.

The few published studies on this method have found that it’s no better at identifying food sensitivities than what would be expected by chance (20).

The extent to which the accuracy of this method varies with the individual skill level of the practitioner is unknown.

Provocation and neutralization test

In this test, a practitioner injects extracts of individual foods suspected to provoke reactions under your skin, typically on your upper arm. After 10 minutes, they check to see if a wheal — an area of raised swelling — forms, which suggests a reaction to the tested food.

If a wheal forms, they give you a second injection of the same food in a dilution five times weaker than the original dose. This is an attempt to neutralize the reaction.

They check your skin again after 10 minutes. If there’s no skin reaction, the administered dose is considered your neutralizing dose.

Finding the neutralizing dose may require several progressively weaker dilutions. You can learn to give yourself injections regularly to desensitize yourself to the food (20).

Given the number of injections you have to get as part of this testing, it could be a slow and potentially painful process.

However, a 2021 narrative review listed this method as not recommended because it has a higher chance of resulting in severe allergic reactions (4).

Electrodermal screening

This test measures changes in your skin’s electrical activity at acupuncture points when presented with various food antigens (21).

For this test, you hold a brass tube (an electrode) in one hand. The tube is connected to a computer that contains digitized frequencies of individual foods. A practitioner presses a computer-connected probe to a specific point in your other hand.

Based on your skin’s electrical resistance when challenged with each food digitally, a numerical reading is generated that corresponds to your degree of reaction to the food.

No published studies have evaluated this technique for testing food sensitivities (20).

Summary

Muscle response testing, provocation tests, and electrodermal screening are additional types of food sensitivity tests.

These generally require more time than tests relying on a single blood draw, and studies on their effectiveness are limited or lacking. Provocation tests may not be recommended due to safety concerns.

Food sensitivity tests come with several caveats. The biggest one is that the tests are not designed for use in diagnosing true food allergies.

If you have a diagnosed allergy to a food, such as peanuts, you should continue to avoid that food, regardless of your results on a food sensitivity test. Even if you think you’ve outgrown a specific food allergy, doctors don’t recommend reintroducing that food on your own.

If you’re considering using these tests to identify food sensitivities, it’s important to understand that they aren’t considered proven, so insurance companies may provide little or no coverage for them. Food sensitivity tests can cost several hundred dollars (7, 20).

Additionally, to verify the accuracy of the test, the results of any food sensitivity test should be cross-checked with what happens in your body when you eat the food.

One possible reason for discrepancies is that most labs doing food sensitivity tests primarily use food extracts from raw foods. However, when food is cooked or processed, new antigens may be created and existing antigens may be destroyed (4, 22).

The purity of each food extract (antigen) used by some labs can also vary, which may skew your results.

Following outdated or inaccurate food sensitivity test results could lead to unnecessary dietary restrictions, potential nutrient deficiencies, and decreased quality of life (20).

Scientists and healthcare professionals are still learning more about food sensitivities. Testing and treatment will likely continue to improve.

Summary

Food sensitivity tests can’t be used to diagnose true food allergies. Though some may help identify food sensitivities, insurance companies often don’t cover the tests. Several factors can affect the validity of the test results.

The best way to identify food sensitivities is through an elimination diet, which involves avoiding suspected problem foods for a period of time and then reintroducing them one by one. It’s important to take detailed notes when using this method.

Lab tests, such as MRT, ALCAT, and IgG antibody tests, may not produce accurate results, though they may be helpful as a tool to help reduce the guesswork.

Still, these tests haven’t been compared to each other in controlled, published studies, so it’s uncertain whether one test is better than another.

At-home tests should not be used to identify a food allergy or to test and reintroduce food allergens you suspect you may have outgrown, as this can be dangerous.

Just one thing

If you suspect you’re having adverse reactions to foods, start by consulting a general medical doctor. They may refer you to a gastroenterologist, an allergist, or another practitioner to rule out conditions such as IBS, celiac disease, and lactose intolerance.