The prevalence of food allergies is on the rise in the United States. And recently, this has corresponded with an increase in the number of tests on the market that tout benefits to “heal your gut” and “understand what foods may be giving you symptoms.” These tests encourage customers to eliminate certain foods regardless of whether they’ve actually experienced GI symptoms from them. 

This article aims to explain the science behind food allergies and to differentiate between food allergies, intolerances, and sensitivities. Finally, we'll conduct a deep dive into commonly sold tests and discern between scientifically credible food allergy panels and those that may not be worth the cash. 

What are food allergies, sensitivities, and intolerances? Why is it essential to differentiate between these three terms? 

People often use the terms “allergy,” “sensitivity,” and “intolerance” interchangeably by mistake. [1] These terms have distinct scientific differences—allergies initiate a response in the immune system, whereas sensitivities and intolerances are generally reactions in the digestive system. 

• The true definition of a food allergy is an immune-system response to the consumption of a particular food mediated by IgE antibodies. 
• A food sensitivity refers to a digestive issue occurring after eating a particular food, such as nausea, bloating, abdominal pain, or diarrhea. These symptoms may result from an imbalanced gut microbiome or intestinal permeability, among other causes.
• A food intolerance is the inability to process or break down a food. A typical example is lactose intolerance, in which an individual cannot process lactose due to the depletion of the enzyme lactase.

Let’s take a deeper dive into the most common food allergies. 

The prevalence of food allergies like "the big eight" allergens—and a new addition

Food allergies and intolerances impact over 85 million Americans today. [2] According to Food Allergy Research and Education (FARE), the top eight most common food allergies (responsible for about 90% of food allergy cases) are cow’s milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, and soy. [3] In April 2021, sesame was added as the ninth major food allergen. Sesame will become required on food labels in 2023. [3] 

According to FARE, there was a 377% increase in treatment of diagnosed anaphylactic (acute hypersensitivity) reactions to food between 2007 and 2016 in the U.S. [2]. Although most food allergies develop in childhood, some people acquire allergies later in life, and some outgrow existing allergies. 

Theories aim to explain why the prevalence of food allergies is on the rise. The first theory is the increase in cleanliness levels, or "hygiene theory." The hygiene theory suggests that, recently, children have had less exposure to immune-mitigating microorganisms, which may make the population more susceptible to developing allergies. Another theory proposes that the rise in food allergies may be attributed to food globalization. These theorists argue that allergies are, at least in part, a result of increased exposure to foods people are traditionally unaccustomed to eating. Additionally, people increasingly consume food products that have changed in manufacturing. [4]

That being said, there are major scientific limitations in proving these theories to be true. Large-scale research schoolrooms are typically required to rationalize the increased prevalence of any condition. However, confirmation trials are unethical, as food allergies are life-threatening.

What tests on the market test for food allergies?

Food allergy symptoms indicate an immune response between food and an antibody, immunoglobulin E (IgE). Read on to learn more about the most common IgE food allergy tests. 

Food challenge test

The gold standard for allergy detection is through a food challenge test. Under the supervision of a physician or allergist, the patient eats foods slowly and in gradual increments while an expert monitors for an allergic reaction. Food challenge tests can confirm a suspected food allergy. [5] Please note, this test must be performed under the supervision of a licensed professional, as symptoms can be severe.

Skin prick testing

Another scientifically valid test confirming a food allergy is skin prick testing, also known as a puncture or scratch test. Here, under supervision, the skin is exposed to suspected allergens and monitored for reactions such as itching, redness, and swelling as part of an IgE response. Skin prick tests have a low rate of false negatives, so negative results indicate no allergy is detected. Skin prick testing is generally considered safe. However, physicians may not recommend skin prick testing if you’ve experienced anaphylaxis, take certain medications, or have other skin conditions. [6]

Total IgE and specific IgE tests

Again, IgE blood testing involves identifying whether an allergen causes an antibody response. A total IgE test describes an overall immune reaction to a potential allergen. These results can include immune responses to substances other than food, for example, pollen, mold, and certain medications. [7] Therefore, a positive IgE result without a clinical allergy can still yield useful information. These results can help individuals understand what foods they should swap with others that don’t produce an immune response. [8,9]

The most common food allergy test, a specific IgE (sIgE) blood test, indicates whether an immune response to a particular food antigen is present. The sIgE test evaluates a panel of 10-20 potential allergens, evaluating specific proteins and their risk of reaction. A positive result from a specific IgE test does not necessarily confirm the presence of a clinical allergy in all cases but rather a sensitization to that particular allergen. [10] SIgE tests are most common because they test for an allergic reaction to specific foods. 

Key takeaway: If you suspect that you have a clinical food allergy, consult with your physician regarding testing. Four scientifically valid allergy tests are a food challenge test, a skin prick test, a total IgE test, and a specific IgE test. 

What food sensitivity tests are on the market? Should I take them?

You may see food sensitivity tests on the market. Here is the science (or lack thereof) behind four common types of food sensitivity tests on the market. 

IgG testing

Many companies send a testing kit to your door, claiming to identify your food allergies or sensitivities from a blood spot IgG test, and recommending food eliminations accordingly. The key issue here? IgG antibodies are “memory antibodies,” meaning healthy individuals produce IgG antibodies in response to recently consumed foods. 

Small studies tout the benefits of eliminating foods that IgG analysis indicates as sensitivities. But it’s important to note that these studies commonly include small sample sizes and can be considered biased due to their inclusion of participants with conditions like IBS—clinically diagnosed cases for which an elimination diet has positive effects on chronic digestive symptoms. 

Further, another study conducted an IgG examination on 73 individuals; 62% tested IgG positive for various foods, but none had an adverse reaction (immediate or delayed) to their IgG-positive foods. These results indicate that IgG levels were a poor predictive tool for intolerances and potential allergies. [11] This study and others reinforce the fact that IgG testing does not produce reliable results. The bottom line: an IgG antibody test does not test for food allergies but rather “memory antibodies” in response to recently consumed foods. 

Hair analysis

Another popular at-home test is hair analysis. Hair testing may be a valid method for toxicology and drug testing. However, companies claim that analyzing hair strands will expose nutritional deficiencies, potential sensitivities, or even allergies through bioresonance. Bioresonance testing inserts a hair sample into a machine with the intent of measuring the “blockage” or “flow of energy” in response to certain substances (allergens, metals, etc.).  

One study took two groups of people—one group with diagnosed fish allergies and another group with no known allergies or intolerances—and sent the samples to three different laboratories. The analysis results showcased multiple discrepancies and lack of reproducibility: the labs failed to correctly identify the “problem food” for the allergy group and further attributed intolerances to the control group. [8] Be wary of claims that hair analysis can pinpoint food allergies through IgE detection: hair does not contain IgE antibodies. 

Mediator release test (MRT)

Another food sensitivity test on the market is a Mediator Release Test (MRT). This test earns its name based on the body’s inflammatory response to foods. A commonality among diet-induced inflammatory responses is that they cause mediator release, e.g., cytokines, leukotrienes, and prostaglandins from various white blood cell components (neutrophils, monocytes, eosinophils, lymphocytes). Interestingly, this release occurs regardless of symptoms. The MRTIII measures the subtle volumetric effects of antigen challenge on individual white cell populations, identifying inflammatory reactions. [12] The MRT is thought to be the most sophisticated food sensitivity test on the market, as measuring mediators provides a more accurate picture than measuring inflammation and is independent of recent exposure. However, there are limitations to the MRT. Robust scientific literature on the test's efficacy is lacking. Additionally, each test yields a positive result for some foods, regardless of the presence or absence of symptoms, making it more useful in those already experiencing symptoms. 

Cytotoxic tests  

Another type of test on the market is cytotoxic assays such as the Alcat test. Here, cytotoxic tests put whole blood samples in contact with food antigens, using the white blood cell reaction to determine sensitivity levels to that particular food. [8] 

A double-blind study aimed to determine the validity and reproducibility of identifying food allergies by cytotoxic test. This study replicated the test for individuals with allergies and those without allergies 56 times. Researchers found that 46 tests did not correlate, and two negative tests had positive histories. [13] This mode of testing presents significant room for error. Not only did this demonstrate the test to be unreliable with little evidence of reproducibility, but the presence of false-negative results has concerning implications for the test recipient. 

Key takeaway: IgG tests do not provide consistent results regarding food sensitivities. Other tests like hair analysis, mediator release test, and cytotoxic tests don’t yield reliable results.

Allergy and sensitivity testing in InsideTracker’s DNA panel

DNA data can predict the individual risk of having gluten and lactose intolerance and a peanut allergy. InsideTracker’s DNA product analyzes specific SNPs to determine the risk level of having these three food-based reactions. However, it’s important to note that these tests do not provide definitive answers; instead, they categorize risk as elevated, average, or reduced. 

Why doesn’t InsideTracker include a food allergy panel?

At this time, InsideTracker does not include an allergy test as a part of its testing panel. Responses to clinical food allergies tend to be severe and immediate and should be discussed with your medical provider. To this end, an allergy test may not reveal novel information to you unless you’re currently experiencing symptoms. However, there is a possibility of a low-grade sIgE response to certain foods you believe to be fine consuming. Identifying these foods may improve your body’s inflammatory response and allow you to try different foods in their place. At this time, the InsideTracker team is monitoring the research on sIgE tests for potential additions. 

During the InsideTracker onboarding process, complete the food questionnaire to accurately reflect the foods you consume to ensure that recommendations accurately represent your allergies and intolerances. Scientific research on topics like allergies is constantly evolving. Therefore, InsideTracker is closely monitoring food intolerance and allergy testing potential future additions. 

A food allergy is a severe medical condition. If you suspect that you have a food allergy, it’s critical to consult with your physician. Also, ensure that the test you’re taking to determine food allergies is held in high scientific regard. 

Key takeaways on food allergies and sensitivities:

• A food allergy triggers an immune-system response to consuming a particular food, while digestive symptoms typically characterize sensitivities and intolerances. 
• The nine most common allergens include cow’s milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, soy, and sesame.
• Tests to uncover a true food allergy include food challenge tests, skin prick tests, IgE, and sIgE tests.
• Food sensitivity tests like IgG, hair analysis, mediator release tests, and cytotoxic tests do not indicate food allergies and are often responsive to the recency of consumed foods, rather than a true sensitivity.
• If you suspect that you have a clinical food allergy, consult with your physician regarding testing.

Michelle Darian, MS, MPH, RD

Michelle Cawley, MS

References:

1. https://pubmed.ncbi.nlm.nih.gov/17077863/ 
2. https://www.foodallergy.org/ 
3. https://www.fda.gov/food/food-labeling-nutrition/food-allergies 
4. https://pubmed.ncbi.nlm.nih.gov/30646188/ 
5. https://pubmed.ncbi.nlm.nih.gov/19500710/ 
6. https://www.foodallergy.org/resources/skin-prick-tests 
7. https://pubmed.ncbi.nlm.nih.gov/32128023/ 
8. https://pubmed.ncbi.nlm.nih.gov/29524991/ 
9. https://www.ncbi.nlm.nih.gov/pubmed/26171168 
10. https://pubmed.ncbi.nlm.nih.gov/25217201/ 
11. https://pubmed.ncbi.nlm.nih.gov/21109748/ 
12. https://www.nowleap.com/mrt-iii-the-future-of-food-sensitivity-testing/ 
13. https://pubmed.ncbi.nlm.nih.gov/787048/