Food sensitivity tests are all marketing and no science.
Wellness companies and people who don't understand immunology are exploiting you.
Food sensitivity tests are not evidence-based indicators of food allergies or 'sensitivities'.
Food “sensitivity” tests are sold direct-to-consumer and marketed as an easy and convenient way to detect an individual’s reactions to certain foods, all from the comfort of your own home. And while they’ve benefited from aggressive marketing and promotion by many in the wellness sphere, they have zero credible science behind them.
Unfortunately, the wellness space is rampant with individuals who mischaracterize immunology for personal benefit. Food sensitivities and these at-home tests are just another example of this. I spoke with Inverse’s
about this very topic back in 2022.In reality, food sensitivity is not a clinical diagnosis.
Before we dig into that, let’s discuss the science behind legitimate food allergies and food intolerances. Food allergies impact around 2-3% of the population, based on legitimate medical diagnosis. However, up to 25% of adults self-diagnose as being ‘sensitive’ or intolerant. The increased rates coincides with the increased presence on the market of ‘food intolerance tests’ which claim to enable you to test your “sensitivity” to hundreds of different foods.
I hate to break it to people, but these are not legitimate.
A food allergy occurs when the body's immune system mistakenly identifies a substance in a food as harmful and mounts an immune-mediated response against it.
Food allergies are rapid immune-mediated reactions to ingestion of specific molecules in given foods. Allergic reactions are generally quick (within minutes to hours) and will occur every time the substance is encountered.
The first time someone is exposed to the food allergen leads to sensitization. During this initial encounter, B cells of the immune system are activated and produce specific antibodies called immunoglobulin E (IgE) to the allergen. For many people, sensitization may not present with any symptoms. (Head to my newsletter about how the immune system develops memory to learn about class switching of B cells). In addition, sensitization also impacts another immune cell type: the mast cells. Once B cells produce those IgE antibodies, those then bind to specific receptors on the surface of mast cells, specifically to a type of receptor known as FcεRI (Fc epsilon receptor I).
The symptoms of an allergy occur upon a subsequent exposure - now that the immune system has developed recognition of this molecule within a food as ‘foreign’, the next encounter leads to a threat signal, activation of the immune response, and an allergic reaction. When the individual is re-exposed to the same allergen, the allergen molecules bind the IgE antibodies already attached to the mast cell surface. This cross-linking of IgE molecules bound to FcεRI receptors on mast cells triggers a signaling cascade within the mast cell, leading to activation of mast cells.
The activation process is called degranulation, which involves the release of stored inflammatory mediators from compartments called granules. The release of these inflammatory chemicals into the surrounding tissue lead to the symptoms of an allergic reaction. The main chemicals released during degranulation are histamine, proteases, leukotrienes, prostaglandins, and cytokines. The released inflammatory mediators induce various physiological responses, including vasodilation (increased blood flow), increased vascular permeability (leakage of fluid and proteins from blood vessels), smooth muscle contraction, and recruitment of other immune cells to the site of activation.
As a result, allergic reactions lead to symptoms such as:
Skin reactions including hives, itching, or eczema
Swelling of the lips, tongue, face, or throat (angioedema)
Gastrointestinal symptoms like nausea, vomiting, diarrhea, or abdominal pain
Respiratory symptoms including coughing, wheezing, nasal congestion, or difficulty breathing (bronchoconstriction)
Anaphylaxis, a severe and potentially life-threatening reaction characterized by a rapid onset of symptoms, including difficulty breathing, a drop in blood pressure, loss of consciousness, and in severe cases, cardiac arrest.
Food allergies are diagnosed by an allergist through two main methods in combination with thorough patient history: a skin test that measures histamine response to potential allergens or a blood test to measure immunoglobulin E (IgE) levels. An increase in IgE levels is associated with an allergic response by the immune system. In some cases, it may even be advised to use one or both of these methods in conjunction with an oral food challenge, in which a potential allergen is ingested in a controlled clinical setting.
A true allergy is also reliable, meaning that it will occur every time a person consumes a given food in any form. Food allergies are more likely to be found and diagnosed in children but can appear at any age. Some individuals may experience relief or changes in immune responses over time or as they age, but broadly speaking, food allergies are considered to be lifelong and currently are not curable.
Treatment involves addressing the histamine response (such as taking antihistamines and other medications), avoiding foods containing the allergen in question, and in more serious cases, having epinephrine auto-injectors available for treatment. Allergy immunotherapy is a longer-term method that can promote tolerance of an allergen, meaning that the individual will no longer have an inappropriate reaction to the substance.
Milk and egg allergies are found to be the most common food allergens globally, but individuals can theoretically develop allergic reactions to an array of substances. Now, remember, it isn’t the food in entirety, but typically a protein of the food that the immune system recognizes as ‘foreign’ instead of benign (scientifically, we call this tolerance).
Milk allergens are often proteins such as casein and whey.
In eggs, allergic reactions can occur to albumin (a protein in egg white), ovomucoid, and ovotransferrin (proteins in egg yolk).
Peanut allergies are often developed against several different seed proteins: Ara h 1, Ara h 2, Ara h 3, and Ara h 6 are most common.
Shellfish allergies are often a result of reactions to proteins in crustaceans, including tropomyosin or arginine kinase.
(There is another class of food allergies that can present hours to days after, such as eosinophilic esophagitis, that are a result of eosinophil immune response, as opposed to mast cells and histamine)
Food intolerances are digestive issues as a result of inability to process certain ingested foods.
Food intolerance refers to difficulty digesting certain foods or substances, leading to various symptoms that may resemble those of food allergies. The biggest difference is that food intolerances are not related to the immune system or immune response to a molecule, but rather, deficiencies in enzymes needed to digest certain substances in a given food.
For example, lactose intolerance occurs when individuals no longer produce sufficient levels of lactase, the enzyme required to digest this particular sugar found in dairy products. Some individuals may have difficulty absorbing fructose, a type of sugar found in fruits, honey, and some sweeteners, as a result of deficient levels of fructose-1-phosphate aldolase, the enzyme that metabolizes that sugar. Galactose intolerance presents with a deficiency or absence of the enzyme galactose-1-phosphate uridylyltransferase (GALT), needed to metabolize galactose, another sugar.
Broadly speaking, food intolerances lead to a variety of gastrointestinal symptoms:
Bloating
Abdominal cramps or pain
Gas (flatulence)
Diarrhea
Nausea
Vomiting (less common)
Symptoms usually occur within 30 minutes to 2 hours and severity often depends on the quantity of the given food consumed.
In contrast, food “sensitivities” are not an indication of anything, aside from exposure to a food.
At-home tests advertised to diagnose food “sensitivities” or “intolerances” are not based on science. Food sensitivity is not a medical diagnosis and can be very vague. Food “intolerance” used outside of digestive enzyme issues is a nebulous term sometimes used to refer to a variety of medical conditions. It often serves as a catchall term to explain a variety of symptoms, including but not limited to headaches, arthritis, congestion, fatigue, and IBS.
Food sensitivity tests measure an entirely different type of antibody called immunoglobulin G (IgG). These are blood tests that you can buy yourself without any involvement from a trained medical professional. They claim to assess the presence of IgG antibodies against different food substances as an indication you have a ‘reaction’ to them.
IgG is an antibody of tolerance, or exposure. It is NOT indicative of being ‘sensitive’ to something.
This is problematic in that IgG is a “memory antibody” that is produced upon being exposed to food substances. It is part of our tolerance pathway: essentially our immune system saying “I recognize this molecule, it doesn’t need to be attacked.”
Food tolerance refers to the body's ability to tolerate and digest food without eliciting an adverse immune response. Unlike food allergies, which involve the immune system reacting against specific proteins in food, food tolerance occurs when the immune system recognizes food as harmless and does not mount an immune response.
The gut-associated lymphoid tissue (GALT) has dendritic cells and regulatory T cells (Tregs) that work together to promote a state of "oral tolerance," where the immune system learns to tolerate harmless food antigens encountered through the diet.
This is a good thing - otherwise we would be having inflammatory responses every time we ate anything. During this process, antibodies such as our mucosal IgA and tolerance-based IgG are produced: and the production of these and the activation of regulatory T cells inhibits the potential induction of that sensitization process, where B cells would produce IgE, bind to mast cells, and develop a future allergic reaction.
IgG production and levels are more indicative of recent history or exposure than a food allergy or intolerance. Someone having detectable IgG antibodies against a given food antigen simply means you’ve been repeatedly exposed to it. In fact, levels of IgG may directly correlate with how frequently you consume a given food.
There is no evidence that IgG is a reliable biomarker for food “reactivity”.
“Food Sensitivity Tests” base their results on IgG antibody levels.
Tests from companies like Everlywell, Viome, Thorne, and others tell you that with a simple finger prick, they can give you results to over 200 foods you’re sensitive to using these IgG levels.
A study that is frequently used to support this unsubstantiated claim based baesd on patients with IBS who took IgG antibody test.
One group eliminated foods identified by the test, while the other group, the control group, used a 'sham diet' that eliminated the same number of foods, but these were not foods identified by the IgG test.
They assessed self-reported symptom scores across 12 weeks among 150 total participants. The authors report a 10% improvement in symptoms in the ‘test’ group compared to the sham group, but both groups reported improvement, and the data spread pretty much overlap.
Additionally, they fail to address important confounders: these are IBS patients. The foods that turned positive in the IgG test are ones routinely avoided for clinical treatment of IBS patients (wheat, barley, corn, beans, and nuts). Many of these foods would be eliminated in cases where a low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are short-chain carbohydrates) diet was implemented clinically for IBS.
In contrast, a large population study (21,305 individuals) in PLoS ONE found that levels of food-specific IgGs were variable both in healthy and in symptomatic Chinese adults. IgG levels were also elevated in otherwise symptom-free, healthy individuals. Again, this reflects that the elevation in IgG in fact represents immunological tolerance, not ‘sensitivity’.
Allergy experts around the world recommend specifically AGAINST using IgG food sensitivity tests.
The European Academy of Allergy and Clinical Immunology (EAACI) states:
"Food-specific IgG4 does not indicate (imminent) food allergy or intolerance, but rather a physiological response of the immune system after exposition to food components. Therefore, testing of IgG4 to foods is considered as irrelevant for the laboratory work-up of food allergy or intolerance and should not be performed in case of food related complaints."
The American Academy of Allergy, Asthma, and Immunology (AAAAI) recommends against using such unproven testing methods, given the lack of validation, quality control, and clinical relevance.
What’s the harm if I’m simply curious?
First: it legitimizes pseudoscience. Why would you want to give money to for-profit companies that are exploiting fundamental misunderstanding of immunology to mislead you?
Second: you are going to avoid foods that there is absolutely no reason to. Because these IgG tests are simply reporting a collection of food molecules that you have initiated tolerance reactions to, these tests are going to ‘flag’ a wide array of things.
According to these company websites, their recommendations are to eliminate those substances and those foods from your diet. So this means anything you consumed recently, or consume frequently, would be something they would suggest you remove from your diet. I’m sure this is obvious, but this is not scientifically indicated and it means you are going to be removing perfectly healthful and nutritious foods with zero reason. Then there is the additional psychological component of health anxiety, avoiding social gatherings, dining out with friends, etc., for fear of encountering foods that these unvalidated tests are telling you to avoid.
And that is the final point: There is ZERO standardization or FDA approval of these tests. These are commercial for-profit labs that develop their IgG tests using “in-house” techniques.
Many have poor reproducibility, meaning that if the same blood sample were analyzed twice, it might show very different results. This is a VERY different process than if you were developing a credible diagnostic test for a legitimate medical condition. Unfortunately, there is a widespread misunderstanding about how clinical diagnostics are created and validated, which has led to a booming industry of a myriad of fraudulent “health” tests including these, at-home allergy tests, metabolic tests, even tests for infectious diseases. None of these are validated or approved by the FDA for use.
If you suspect you may have a food allergy or intolerance, you should see a legitimate allergist or immunologist for credible evaluation.
Over- and mis-diagnoses of food allergies, particularly brought on by at-home tests that may not be appropriate, lead to a lot of confusion, unnecessary diet restriction, or delay of medical care and diagnosis of other medical conditions.
At-home food sensitivity tests have a current market worth $159.3 million in the US alone, and that number is growing rapidly based on promotion from wellness influencers and aggressive marketing campaigns. Unfortunately, there is zero evidence to support the use of these tests, and their false results cause a lot of unnecessary harm.
Steer clear of these at-home health tests promising things that are not based in reality.
As always, thanks for joining in the fight for science!
Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, roadblocks to scientific progress that improve food and crop sustainability, it’s needed now more than ever.
Your local immunologist,
Andrea
Remember my friends taking these tests which made them avoid many foods. The problem was that none of these foods caused them any digestive problems 🤷♀️