Should You Get a Food Sensitivity Test?

Food sensitivity testing can be a useful tool when it comes to improving your health, but it’s important to understand exactly what a food sensitivity test can tell you (and what it can’t). 

Food sensitivity tests have their benefits and limitations, and I’m going to break them down for you here, along with key insights from working with patients and these tests in my functional medicine telehealth clinic. 

Food Sensitivities vs. Intolerances vs. Allergies

There’s a lot of confusion around what a food sensitivity actually is, in part because the term is often used interchangeably with terms that mean other things, like food intolerances or allergies. 

I don’t mean to get overly hung up on terminology, but I do think that understanding the differences between these types of relationships to foods is helpful, especially if you’re considering a food sensitivity test. 

Food sensitivities and allergies are similar because they’re both mediated by the immune system. They both involve the immune system reacting to a food by releasing immunoglobulins (also known as antibodies), protective proteins that are meant to help the body attack foreign invaders. 

Allergies and sensitivities are differentiated based on the type of immunoglobulin that is released. 

In the case of most food allergies, the immune system releases immunoglobulin E (IgE), which acts very quickly and typically produces classic allergy symptoms like a rash or hives, swelling, itchy eyes, or in some cases, more severe reactions including anaphylaxis. (1) 

Food sensitivities are generally mediated by immunoglobulin G (IgG) or sometimes immunoglobulin M (IgM). The response is usually more delayed and can be difficult to pinpoint as symptoms are nonspecific, ranging from fatigue and brain fog to skin issues, bloating, and joint pain. 

READ MORE: Are You Eating These 13 Foods That Cause Inflammation? 

Food intolerances, by definition, are not directly mediated by the immune system. They’re characterized instead by a deficiency in the digestive enzymes needed to break down a particular kind of food. 

For example, a lactose intolerance occurs when you lack the lactase enzyme. Depending on the intolerance, the gut and immune system may still be involved to different degrees, but the immune system isn’t directly reacting to a food. 

What Is a Food Sensitivity Test? 

A food sensitivity test is a type of lab test that looks at immunoglobulin G (IgG) and sometimes IgM or IgA reactions to a list of common foods. These are blood tests, usually involving a blood draw at a lab, or in some cases from an at-home finger prick. 

After the lab has finished analyzing your sample, you receive a report that shows which foods you’re most and least reactive to at the time of the test (that last part is important, and we’ll talk about it more below). 

The purpose of the test and the report is to help you understand which otherwise healthy, real foods you may unknowingly have sensitivities to, and to allow you to build a personalized eating plan around this information. 

Food sensitivity tests look specifically at immune mediated food sensitivities, not intolerances (enzyme deficiencies). 

Different lab options are available looking at different foods (usually the more detailed or the more foods being tested, the higher the cost of the test). More specialized options include gluten cross-reactive testing, which tests for specific foods that can mimic or be mistaken for gluten by the immune system. 

Benefits of Food Sensitivity Testing

Food is foundational when it comes to health and healing, and many people do have hidden food sensitivities or triggers. So the primary benefit of food sensitivity testing is that it can help you to identify these triggers, and set you on a path towards a more bioindividualized eating plan, when interpreted with context. 

I’ve had some patients who have discovered one or two problematic foods using food sensitivity testing, and who have felt ten times better just by eliminating those foods. These are often people who have already generally cleaned up their diets and lifestyles and are feeling pretty good, but something is still missing. 

I also find specialized food sensitivity testing particularly helpful for those with immune-mediated reactions to gluten: testing for cross-reactive foods (foods that can be mistaken for gluten by the immune system because of the relative similarity of their proteins) can help identify why someone is still experiencing gluten-like reactions after eliminating gluten. 

Limitations and Downsides of Food Sensitivity Testing

There are a number of limitations and downsides of food sensitivity testing. I’m not sharing these to discourage you from testing: we use these tests in our functional medicine telehealth practice, and they have their time and place. But I do think it’s important to understand where and when they can fall short. 

First, food sensitivity testing is naturally limited by the fact that it doesn’t test for intolerances. This type of testing also doesn’t identify the patterns that are behind a lot of food reactions. 

For example, many people with SIBO (small intestinal bacterial overgrowth) and other gut imbalances experience symptoms from eating foods high in FODMAPs, fermentable carbohydrates that resist digestion and act as fuel for gut bacteria. 

Other examples of patterns not identifiable by an FST would be sensitivities to salicylates, lectins, or high histamine foods. 

More importantly, food sensitivity testing, especially if not interpreted or understood properly, can lead to a lot of discouragement, anxiety or fear around food, or orthorexia (an unhealthy obsession with healthy eating). 

We see so many patients come in with test results from at-home food sensitivity tests (or tests run by other healthcare providers) where almost every food is in red (indicating that it’s a “bad” food for them). These patients often tell us that they’re down to eating just three or four foods. 

But while it might seem contradictory, in our experience the more foods that are flagged as “bad”, the less likely it is that the foods are actually the problem. Instead, this is usually a sign of leaky gut and a hyperreactive immune system. (2) These underlying issues are what really need to be resolved, and focusing instead on eliminating more and more foods can distract from the real problem (and bring up new problems). 

Digging Deeper For the Root Cause

Food sensitivity testing can certainly be a tool within the toolbox. But when we’re seeing lots of food reactions, and particularly to foods that don’t typically cause reactions like fruits and vegetables, we need to dig deeper to find out what’s underlying this reactivity. 

Something is causing the immune system to be hypervigilant or overreactive, and triggering widespread inflammation. Our job in functional medicine is to figure out what that is. 

Underlying causes may include any of the following, and often a combination: 

• Increased intestinal permeability (leaky gut) 
• Autoimmunity (3)
• SIBO (small intestinal bacterial overgrowth) or gut dysbiosis (imbalance within the gut microbiome) (4) 
• Mold toxicity 
• Bacterial, viral, or parasitic infections 
• Yeast or fungal overgrowth 
• History of trauma or chronic emotional or psychological stress (5)  

To help determine what’s going on, we look at your medical history and individual health profile, and often run additional labs to uncover missing pieces. 

Depending on these individual factors, additional tests may include: 

• SIBO testing 
• Gut microbiome testing
• Leaky gut/zonulin testing 
• Autoimmune and inflammatory markers 
• Testing for toxins including mycotoxins (from mold) 
• Cortisol and other hormone panels 

On the other hand, if you’re only seeing a small handful of foods that are causing reactions, especially if you’re not otherwise symptomatic, these may just be true sensitivities. It’s all about context. 

Healing and Retesting 

Because most cases of multiple food sensitivities are really about the immune system and gut health, not about the foods, when we heal these underlying issues we often find that most of the food sensitivities go away. 

So, while it may be a good idea to avoid foods tagged as sensitive while you’re healing these root causes, know that you usually won’t need to avoid them forever—the goal is to have you eating as many healthy whole foods as possible. 

I often recommend retesting a year or two after your original FST, especially once you’ve worked on your digestive health and immune system balance. You will likely see a much more encouraging list, and feel more confident about reintroducing foods you’ve cut out. 

Is an Elimination Diet the Best Test? 

An elimination diet is in many ways the best test for identifying food triggers. It involves eliminating potentially problematic foods for a month or sometimes longer, and then reintroducing them one at a time and monitoring any symptoms that arise. 

Elimination diets are helpful because they help you listen to your body and see which foods make you feel well and unwell, whether it’s an IgG-mediated sensitivity, an IgE-mediated allergy, an intolerance related to enzyme deficiency, or something else. 

However, a standard elimination diet might miss certain hidden food sensitivities, especially to things like fruits and vegetables that you’re not necessarily eliminating. 

There is also still the same caveat that if you notice a lot of sensitivities, there is probably something going on beneath the surface that needs to be figured out. 

Food Sensitivity Tests Can Help With the Puzzle

Overall, food sensitivity tests can offer some clinical value, if they’re being interpreted as part of the puzzle. They shouldn’t be treated as definitive guides to your diet: they’re really a snapshot in time, showing you what the immune system, in its current state, is reacting to right now. 

When not interpreted properly or with context, they can cause unnecessary fear and anxiety around food. 

But when taken with a grain of salt, food sensitivity tests can help guide short-term changes, while you work to uncover and address the root causes of immune system reactivity. 

For guidance that factors in your bioindividuality and the whole puzzle, you can book a consultation with our functional medicine telehealth team. We’d love to help you put the pieces together. 

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe.

FAQs

Sources

• Bégin, P., Waserman, S., Protudjer, J. L., Jeimy, S., & Watson, W. (2024). Immunoglobulin E (IgE)-mediated food allergy. Allergy, Asthma & Clinical Immunology, 20(Suppl 3), 75.
• Vita, A. A., Zwickey, H., & Bradley, R. (2022). Associations between food-specific IgG antibodies and intestinal permeability biomarkers. Frontiers in Nutrition, 9, 962093.
• Coucke, F. (2018). Food intolerance in patients with manifest autoimmunity. Observational study. Autoimmunity Reviews, 17(11), 1078-1080.
• Caminero, A., Meisel, M., Jabri, B., & Verdu, E. F. (2019). Mechanisms by which gut microorganisms influence food sensitivities. Nature Reviews Gastroenterology & Hepatology, 16(1), 7-18.
• Buret, A. G. (2006). How stress induces intestinal hypersensitivity. The American Journal of Pathology, 168(1), 3-5.