Sarah Glinski, RD
Food sensitivities are a common health issue that affect up to 20% of the population. Food sensitivity symptoms include digestive discomfort, headaches, brain fog, skin issues, and fatigue. Unlike food allergies, which trigger an immediate immune response and allergic symptoms, food sensitivities often cause delayed reactions, making them harder to pinpoint.
While an elimination diet is the gold standard for identifying food sensitivities, there's a growing interest in food sensitivity testing to identify problematic foods. Testing methods, such as IgG, IgG4, IgA, and Leukocyte Activation Testing (LAT), aim to detect immune responses to different foods. However, not all tests are equally reliable, and many remain controversial in the healthcare industry.
Read on to learn how different food sensitivity tests work, the current evidence for using at-home food sensitivity tests, and tips for interpreting test results.
Understanding Food Sensitivities
While many use the terms interchangeably, food sensitivities and food intolerances differ from food allergies.
Food Allergies
Food allergies describe an immune system response involving IgE antibodies (a type of immune cell). When a person has a food allergy, the body mistakenly identifies a food protein as harmful and produces IgE antibodies.
Food-related allergy symptoms often start just minutes after eating but could occur up to two hours after a meal. Reactions can be severe and include hives, shortness of breath, dizziness, and anaphylaxis (a life-threatening reaction that can disrupt breathing). Common food allergens include peanuts, shellfish, and dairy.
To diagnose food allergies, you'll undergo a variety of tests, including a detailed medical history, a skin prick test, blood tests that measure IgE, and in some cases, an oral food challenge where you eat the suspected food under medical supervision to observe reactions. Once you receive an allergy diagnosis, you must avoid that food to prevent an allergic reaction.
Food Sensitivities
Food sensitivities also involve the immune system, but they don't involve IgE antibodies. Some research shows that food sensitivities are associated with increased intestinal permeability (sometimes colloquially described as "leaky gut").
Food sensitivity symptoms can manifest in various ways, including:
- Digestive issues, like gas, bloating, diarrhea, constipation, nausea, and vomiting.
- Skin reactions, like eczema, rashes, and acne.
- Neurological symptoms, like headaches, migraines, and brain fog.
- Respiratory issues, like congestion and sinus problems.
- Joint and muscle pain, including inflammation and stiffness.
- Fatigue and mood changes, like anxiety, irritability, and depression.
Food Intolerances
Unlike food allergies and food sensitivities, food intolerances don't involve the immune system. They typically result in digestive symptoms like gas and bloating. A common type of food intolerance is FODMAP intolerance. This occurs when people have trouble tolerating fermentable carbohydrates like fructans and galacto-oligosaccharides (GOS) since the human body doesn’t produce enzymes needed to break them down. Other potential food intolerances include gluten, histamine, caffeine, alcohol, sulphites, salicylates, monosodium glutamate (MSG), and lactose intolerance.
Troublesome food sensitivity symptoms can lead to avoidance of multiple foods. If many food groups are suspected of triggering symptoms, this could result in nutrient deficiencies, disordered eating behavior, an eating disorder, and food-related stress. Therefore, correctly identifying which specific food triggers symptoms is crucial to ensuring people aren't avoiding foods unnecessarily.
Types of Food Sensitivity Tests
Food sensitivity tests aim to identify the foods that may trigger symptoms like digestive issues, inflammation, skin problems, and brain fog. However, many are unproven diagnostic tests that vary in accuracy, methodology, and scientific backing.
Before diving into how these tests work, you need to understand a few terms related to the immune system. First, we have immunoglobulins. Immunoglobulins are antibodies—proteins made by the immune system to help identify and neutralize harmful substances like bacteria and viruses. There are several different types of immunoglobulins, each with a different role.
We also have leukocytes (white blood cells). These cells are key players in the immune system and help defend the body against infections and harmful invaders like bacteria and viruses. When they come into contact with something they perceive as dangerous, leukocytes release inflammatory chemicals (mediators) to help recruit more immune cells to the area and enhance the body's defences.
Many food sensitivity tests measure the amount of immunoglobulins (antibodies) in the blood or the activity of white blood cells to detect potential reactions to certain foods.
IgG Testing
Immunoglobulin G (IgG) testing measures the levels of IgG antibodies produced in response to specific foods. It's based on the premise that high IgG levels indicate food sensitivity. To complete the test, a blood sample is analyzed for reactivity to a panel of foods.
Another type of IgG testing is IgG4 testing. IgG4 is a subtype of IgG. It's considered a "blocking antibody" because it helps the body tolerate substances rather than react to them. High IgG4 levels usually mean your immune system has adapted to a food, not that you're sensitive to it. This makes IgG4 testing less helpful in identifying food sensitivities. However, if IgG4 levels are high, they could be a sign of an actual food allergy, so an IgE test may be needed to check for true allergic reactions, like a wheat or dairy allergy.
IgA Testing
IgA testing measures immunoglobulin A (IgA) antibodies produced in response to foods. IgA is the primary immune defence in the gut lining and mucosal surfaces (like your nose and mouth). This type of testing is used to assess gut inflammation and immune responses in the mucosal surfaces. High levels of IgA in the blood can be indicative of inflammatory disorders like IgA nephropathy (a type of kidney disease), AIDS, and several autoimmune diseases.
However, the role of IgA in food sensitivities is less clear, with studies showing that a deficiency of IgA is associated with true food allergy. In addition, the location of IgA may be important, with studies showing that IgA in the blood increases in mice experiencing anaphylaxis (an allergic reaction). In contrast, IgA in the stool increases in mice tolerant (not sensitive or allergic) to a food allergen. Overall, IgA testing may be more useful in true food allergy testing than food sensitivity testing.
Leukocyte Activation Testing
Leukocyte Activation Testing (LAT) measures changes in white blood cells (leukocytes) when exposed to food antigens (substances that trigger your body's immune system to respond). The Mediator Release Test (MRT) is a common LAT test that measures inflammation-causing chemicals like histamine and cytokines released by immune cells. MRT claims to detect food sensitivities more accurately than IgG-based tests.
CellTolerance Test
The CellTolerance test looks at the cells of the mucosal barrier (the protective layer lining your intestines that keeps harmful substances out of your bloodstream) to see whether foods are causing damage. It's based on a technique called confocal laser endomicroscopy (CLE) — a high-tech imaging method that lets doctors see real-time, microscopic details of the gut lining during an endoscopy (a procedure where a tube with a small camera on the end is inserted into your digestive tract). This can help them detect issues like inflammation or food sensitivities more accurately.
The CellTolerance test is based on the premise that many people with IBS have atypical food allergies that are not associated with IgE (which is associated with true food allergies). A 2019 study looking at the effectiveness of CLE for diagnosing food sensitivities found that over half of the IBS patients in the study reacted to certain foods and that avoiding those foods led to lasting symptom relief.
Evaluating the Accuracy and Reliability of Food Sensitivity Tests
When it comes to food sensitivity tests, no single test is 100% accurate. The gold standard for identifying food sensitivities remains an elimination diet followed by the systematic reintroduction of suspected trigger foods (such as the low FODMAP diet).
While IgG-based food sensitivity tests are widely available, they remain controversial due to inconsistent scientific support. There is little scientific evidence that IgG testing can accurately determine food sensitivities and does not always correlate with symptoms. This is because the presence of IgG can indicate normal food exposure rather than sensitivity. In other words, if high IgG levels are detected in response to a food, it simply means you've recently eaten that food. A study from 2018 found that there was no association between levels of IgG in the blood and perceived intolerance to milk and wheat.
The American Academy of Allergy, Asthma, and Immunology recommends against using IgG or IgG4 testing to diagnose food intolerances or sensitivities, as misinterpretation of the results can lead to unnecessarily restrictive diets that could lead to nutritional deficiencies or an eating disorder.
IgA testing is also controversial, with few studies indicating it can effectively diagnose food sensitivities. However, the IgA anti-transglutaminase (TTG) testing used as part of the diagnostic process for celiac disease (an autoimmune disease where the immune system mistakenly reacts to gluten) is a validated screening test.
MRT testing is based on the antigen leukocyte antibody (ALCAT) test. Overall, there is a lack of peer-reviewed research regarding the validity of these tests, and an expert panel overseeing guidelines for the diagnosis and management of food allergies in the U.S. recommends against its use.
Finally, the science behind the CellTolerance test is relatively new, with some open-label studies showing symptom relief when patients exclude the food that triggered a reaction in their gut lining. However, more rigorous research is needed to understand the role of gut lining changes in response to food in IBS.
If you do still want to use a food sensitivity test, it should be used alongside detailed symptom tracking in a food diary and professional medical advice from a registered dietitian or healthcare provider.
Top Food Sensitivity Testing Options
Here are some of the most popular food sensitivity testing kits and options currently available. Know that this is simply a summary of common products and not an endorsement or recommendation to use any.
US BioTek Food Sensitivity Panels
The US BioTek Food Sensitivity Panels measure IgG, IgG4, and IgA antibodies in the blood to identify potential food sensitivities (in other words, they measure the body's immune response to different foods).
The test requires a small blood sample, which is analyzed in a lab for reactivity to up to 240 different foods, depending on the panel chosen. They also have specialized diet panels, including foods commonly eaten in different cuisines, such as Japanese and Mexican foods. Finally, they offer vegetarian food sensitivity panels that include either 96 or 198 vegetarian foods.
The test uses a scientific technique called ELISA (enzyme-linked immunosorbent assay). This test detects specific immune system proteins (like IgG, IgG4, and IgA) in response to different foods and food chemicals. The test then measures how much antibody is present using a light-based analysis.
Results categorize foods based on immune response levels. Your healthcare provider can view and download the blood sample results through US BioTek's Clinician Portal. Once they have the test results, you can schedule a time to discuss them with your provider.
Everlywell Food Sensitivity Test
The Everlywell Food Sensitivity Test is an at-home food sensitivity test that measures IgG antibody levels in response to different foods. You can order the test online. To take the test, you'll collect a small blood sample via a finger prick and send it to a certified lab for analysis. Your skin prick test results will be reviewed by a doctor licensed in your state before being sent to you.
The test examines reactions to 96 or 204 foods, depending on the selected panel. It provides a report ranking foods based on IgG reactivity. You then have the option to follow a two-part elimination diet based on the results.
InFoods by Biomerica
The InFoods test by Biomerica is a blood test that checks for immune reactions to 18 foods associated with IBS symptoms. It works by detecting IgG antibodies in the blood. While IgG antibodies are not indicative of food sensitivity, the creators of the test claim that the methodology used to choose the foods tested is more rigorous and evidence-based than other IgG-based food sensitivity tests.
MRT by Oxford Biomedical
The Mediator Release Test (MRT) is a blood test that measures your body's reactions to over 170 foods and food chemicals. It's designed to be used in conjunction with their Lifestyle Eating and Performance (LEAP) anti-inflammatory eating plan.
The MRT test is based on the premise that food sensitivities cause inflammation, which leads to the release of inflammation-causing molecules from white blood cells (leukocytes). Your blood sample will be exposed to different foods and food additives and monitored for changes in your white blood cells. If your white blood cells react to the food, they will shrink. This is accompanied by an increase in blood plasma volume (the amount of the liquid portion of your blood).
Once you receive your test results, it's recommended that you follow the LEAP elimination diet. This diet eliminates foods the test indicates you may be sensitive to, then slowly reintroduces them while monitoring for the return of symptoms.
CellTolerance Test
To complete the CellTolerance test, you first meet with a registered dietitian to assess your food patterns, reactions, and suspected intolerances. Then, an endoscopist and gastroenterologist look at the cells of your gut lining with the list of suspected allergens. The suspected allergens are applied to your intestines one at a time during a 15 to 30-minute procedure.
After the procedure, the endoscopist will record the positive test results and give that information to your dietitian. Your dietitian will then recommend which foods to include and exclude based on those results. You'll have follow-ups with your dietitian and/or psychologist every 30 days for three months to make adjustments to your diet.
Food Sensitivity Tests At-A-Glance
What to Consider When Choosing a Food Sensitivity Test
If you're experiencing digestive issues and suspect food sensitivity is to blame, you may be considering one of the food sensitivity tests listed above. However, not all tests are created equal. Here are some key factors to consider before choosing the best food sensitivity test for your needs.
Test Comprehensiveness
Some tests screen for a few dozen foods, while others analyze hundreds. When choosing a food sensitivity test, consider the variety of foods tested to ensure it includes foods you commonly eat.
Accuracy and Scientific Validity
Many at-home food sensitivity tests rely on IgG antibodies, which are not a definitive marker for food sensitivities. The body produces IgG antibodies whenever it's exposed to a food, so the presence of IgG on a home food sensitivity test simply indicates food consumption, not an adverse reaction. Because of this, IgG-based tests often lead to unnecessary food restrictions without addressing the root cause of symptoms.
Cost and Accessibility
At-home food sensitivity rests range in price, depending on the type of test and the number of foods analyzed. Some offer payment plans or insurance reimbursement, but many are out-of-pocket expenses. In some cases, you may be able to use your health savings account to pay for the test.
It's also important to note that being more expensive doesn't necessarily mean being more accurate. It's essential to consider the value of consulting with a healthcare provider instead of relying solely on test results to tell you if you have food sensitivities.
How to Interpret Test Results
Interpreting the results of food sensitivity tests can be difficult, as most at-home tests measure IgG antibodies, which indicate food exposure rather than an accurate test of true sensitivity. If a test shows high IgG levels for a food, it doesn't necessarily mean you need to eliminate it. Instead, use the results as a guide for an elimination diet, where you temporarily remove potential food triggers and gradually reintroduce them to assess whether they're behind your symptoms.
Because food sensitivity tests lack strong scientific validation, it's crucial to consult a healthcare professional like a registered dietitian before making major changes to your diet. They can help you interpret the results in context, rule out other potential causes of your symptoms, and create a balanced meal plan that avoids unnecessary food restrictions that could lead to nutrient deficiencies, disordered eating, and stress related to food.
Remember, the gold standard for identifying food sensitivities is an elimination diet, which can be challenging if you don't consult a healthcare professional.
Finding the Best Food Sensitivity Test and How FODZYME Can Help
Most food sensitivity tests on the market lack strong scientific backing and may not provide accurate or reliable results. Many rely on IgG antibody testing, which primarily indicates exposure to a food rather than an actual sensitivity. Because of this, the gold standard for identifying food sensitivities remains an elimination diet, where potential trigger foods are systematically removed and reintroduced while tracking symptoms. Working with a healthcare professional like a registered dietitian can help ensure this process is done safely and effectively.
Once you've identified your food sensitivities, managing them can be a challenge. That's where FODZYME comes in. As a targeted enzyme supplement, FODZYME helps break down fermentable carbohydrates (FODMAPs) that can cause digestive problems in susceptible individuals, allowing them to enjoy a more varied diet with fewer discomforts. Explore how FODZYME can support your digestive health today!