Sometimes certain foods can make you feel unwell, regardless if they’re healthy or not.
They may trigger any number of food sensitivity symptoms, such as headaches, digestive issues, joint pain or skin problems.
It can be tricky to figure out which foods are the culprits, as food sensitivity reactions are often delayed by a few hours or longer after eating the foods.
To help identify potentially problematic foods, some health practitioners offer food sensitivity tests.
Here’s a closer look at what food sensitivities are and the best tests to identify them.
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.
In contrast, food sensitivities and food intolerances generally are not life-threatening but may make you feel bad.
|Food allergy||Food sensitivity||Food 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 involved||Top 8 most common: milk, egg, peanut, tree nuts, wheat, soy, fish and crustacean shellfish.||Varies from person to person and may include foods you eat often.||Fermentable carbs (FODMAPS): milk (lactose), legumes and certain vegetables, fruits, grains and sweeteners.|
|Onset of symptoms after eating the food||Rapid, often within minutes.||Within a few hours but may be delayed up to a few days.||Within 30 minutes to 48 hours after eating.|
|Examples of symptoms||Trouble swallowing or breathing, nausea, vomiting, hives. Can result in anaphylaxis.||Headaches, joint pain, digestive issues, skin issues, an overall feeling of being unwell.||Most common are digestive issues: bloating, excess gas, gut pain, diarrhea, constipation.|
|Amount of food needed to cause symptoms||Tiny.||Varies depending on your degree of sensitivity.||Generally worse with larger amounts of problem foods.|
|How it’s tested||Skin prick tests or blood tests of IgE levels to specific foods.||Many tests are available, but their validity is uncertain.||Breath tests may identify fermentable carb intolerances (lactose, fructose).|
|Age of diagnosis||Commonly in infants and young children, but adults can also develop them.||Can appear at any age.||Varies, but lactose intolerance is most likely in adults.|
|Prevalence||1–3% of adults; 5–10% of children.||Uncertain but suspected to be common.||15–20% 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.||May be able to consume a food again without symptoms after you avoid it for several months and address any underlying issues.||Can minimize symptoms by limiting or avoiding problem foods 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.
The gold standard for identifying food sensitivities is an elimination diet followed by an “oral challenge” of eating the eliminated foods one by one after a period of avoidance to determine your reaction — ideally without you knowing what’s being tested (4).
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 masked or hard to detect.
When you stop eating a problem food, you may have temporary withdrawal symptoms. You might have to follow an elimination diet for about two 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 must know the ingredients of everything you eat, which makes eating out difficult.
The foods you avoid in an elimination diet vary. Some practitioners may only have you eliminate foods suspected to be a problem, such as dairy and wheat products.
Others may have you eliminate all but a few foods for a short period, such as two weeks, and then slowly reintroduce them.
To reduce the guesswork as to which foods are problematic, some practitioners first give you a food sensitivity test to help guide your elimination diet.
Importantly, you should never attempt to reintroduce a food on your own if you have a true allergy. If you suspect you may have outgrown a food allergy, discuss appropriate testing with your allergist.
Summary The gold standard for identifying food sensitivities is an elimination diet followed by a methodical “oral challenge” of trying the eliminated foods one by one after a period of avoidance. Some practitioners use food sensitivity tests to home in on problem foods.
Since then, immunologists have improved and automated the testing technology. Two cell-based blood tests available are MRT and ALCAT.
Though some practitioners have reported that they find these tests useful, published studies on the tests are limited (9).
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 solids (white blood cells) to liquid (plasma) ratio of your blood sample, which is measured to determine your reactivity to the food (9).
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, trained in the test and its interpretation.
A small study presented at an American College of Gastroenterology conference found that people with irritable bowel syndrome (IBS) who followed an elimination diet based on MRT results for at least one month reported a 67% improvement in gut issues, such as diarrhea.
However, there was no control group in this study, nor has it been published in full. Furthermore, PubMed, a large database that indexes published medical studies, lists no studies on the MRT test.
Antigen Leukocyte Cellular Antibody Test (ALCAT)
The ALCAT test is the predecessor of the MRT test, but many healthcare practitioners and labs still offer it.
To assess what foods may be provoking a reaction for you, it only measures changes in the sizes of your white blood cells (rather than changes in the solids to liquid ratio) when exposed to individual food antigens, which may decrease accuracy.
When people with IBS followed a diet based on their ALCAT test results for four weeks, they reported twice the reduction in certain IBS symptoms, such as abdominal pain and bloating, compared to people following a placebo diet (10).
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 (10).
Summary Cell-based blood tests, including the MRT and ALCAT, assess changes in your white blood cells when exposed to food antigens. Some practitioners report the tests are helpful in identifying food sensitivities, but both 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 compared to 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 migraines (11, 12, 13, 14).
Still, many scientists advise people not to use IgG food sensitivity tests, saying that 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 (15, 16).
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 poor reproducibility, meaning that if the same blood sample were analyzed twice, it might show very different results.
It’s recommended that you only use an IgG test if it evaluates your blood sample twice with each antigen in side-by-side duplicate testing to minimize errors in your results.
Blood spot testing is a variation of the traditional IgG testing that requires a phlebotomist to draw blood from a vein in your arm. Instead, it uses a small blood sample from your finger that’s collected on a special test card. It’s unknown if this method is reliable (4).
Summary Tests that evaluate your levels of IgG antibodies against foods are available under various brand names and may help identify foods involved in symptoms like IBS and migraines. Accuracy is improved if a lab does side-by-side duplicate testing.
Several other tests to check for food sensitivities may be used by some alternative practitioners, such as chiropractors, naturopaths and environmental medicine doctors.
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.
In the few published studies of this method, it was found to be no better at identifying food sensitivities than what would be expected by chance (17).
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, extracts of individual foods suspected to provoke reactions are injected beneath your skin, typically on your upper arm. After 10 minutes you are checked to see if a “wheal” or raised swelling forms, which suggests a reaction to the tested food.
If a wheal forms, you’re given a second injection of the same food but in a dilution that’s five times weaker than the original dose. This is given to try to neutralize the reaction.
You’re checked again after 10 minutes. If there’s no skin reaction, the administered dose is considered your neutralizing dose.
It may require several progressively weaker dilutions to find the neutralizing dose. You can be taught to give yourself injections regularly to desensitize you to that food (17).
When people were given provocation skin injection tests for five food sensitivities that were previously confirmed by oral challenges, the results matched 78% of the time (18).
Given the number of injections you have to get as part of this testing, it could be a slow and potentially painful process.
This test measures changes in your skin’s electrical activity at acupuncture points when presented with various food antigens (19).
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 (17).
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. In addition, studies of their validity are limited or lacking.
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.
If you’re considering using these tests to identify food sensitivities, realize that they aren’t viewed as proven, so insurance companies may provide little or no coverage for them. Many of the tests cost several hundred dollars (9, 17).
Additionally, to verify accuracy, 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 (20, 21).
The purity of each food extract (antigen) used by some labs also varies, which can skew your results.
Also note that food sensitivities can shift over time based on what you’ve been eating. A test taken six months or a year ago may no longer reflect your current state of reactivity to specific foods (4).
Following outdated or inaccurate food sensitivity test results could lead to unnecessary dietary restrictions, potential nutrient deficiencies and decreased quality of life (17).
Lastly, scientists and health practitioners have more to learn about food sensitivities. Testing and treatment will continue to evolve with ongoing analysis.
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, and sensitivities can shift over time.
An elimination diet followed by methodically trying eliminated foods one by one after a period of avoidance is the best way to identify food sensitivities.
Lab tests, such as MRT, ALCAT and IgG antibody tests, all have limitations and their accuracy may vary by lab. Yet, they may help reduce the guesswork.
Still, these tests haven’t been compared against each other in controlled, published studies, so it’s uncertain whether one test is better than another.
If you suspect you’re having adverse reactions to foods, start by consulting your doctor, who may refer you to a gastroenterologist, allergy doctor or another practitioner to guide you.