Dr. Michael Ruscio, DC is a clinician, Naturopathic Practitioner, clinical researcher, author, and adjunct professor at the University of Bridgeport. His work has been published in peer-reviewed medical journals and he speaks at conferences around the globe.
What Food Allergy Test Results Do and Don’t Tell You
It’s tempting to imagine a food allergy test kit would help you figure out why you’re having food reactions. However, most food sensitivity test kits only check for one type of food reaction among many and haven’t been shown to be accurate in research studies.
The best food allergy test is actually a targeted elimination diet that removes common food allergens. In this article, we’ll explore how food allergies work, what food allergy tests can and can’t tell you, and why an elimination diet is actually the best food allergy test.
What’s the Difference Between Food Allergies, Sensitivities, and Intolerances?
To better understand food allergy tests and what their results mean, let’s explore food allergy, sensitivity, and intolerance symptoms, define these terms, and explain the differences between them.
Symptoms of Food Allergy, Sensitivity, & Intolerance
The symptoms of food allergies, sensitivities, and intolerances can affect many parts of your body. Symptoms can happen immediately after eating a food, or in some cases several days after consumption. Here is a partial list:
Digestive and IBS symptoms such as bloating, gas, stomach pain, diarrhea, or constipation
Allergy symptoms, such as hives, sneezing, watery eyes, sinus congestion, or difficulty breathing
Pain symptoms including joint pain, body pain, or headaches
Brain symptoms such as brain fog, memory problems, anxiety, or depression
Skin symptoms such as rashes, hives, eczema, or acne
Now let’s explain the difference between the three types of food reactions.
A food allergy is a sudden, and sometimes life-threatening allergic reaction (anaphylaxis) to specific foods.
Food allergies commonly cause hives, itchy eyes, nose, throat, or ears, and in severe cases, may result in a swollen tongue, difficulty breathing, or death. People with food allergies may have severe reactions to foods like peanuts, tree nuts, and shellfish.
Food allergies are an immune reaction triggered by IgE antibodies (one branch of the immune system) and are tested with skin prick tests.
Food sensitivities are also an immune reaction. However, symptoms may be delayed and are often vaguer than food allergies.
Food sensitivity symptoms can include digestive symptoms like bloating, abdominal pain, diarrhea or constipation, or non-digestive symptoms like fatigue, joint or muscle pain, brain fog, or headaches.
Common food sensitivities include foods like gluten, dairy products, soy, nightshade veggies like tomatoes and eggplant, or eggs, for example. Non-celiac gluten sensitivity is an example, which may cause digestive and non-digestive symptoms, like bloating, gas, fatigue, brain fog, or headaches .
Food sensitivities may be caused by an immune reaction to IgG antibodies (another branch of the immune system), inflammation from bacterial overgrowth in the gut , leaky gut , or other types of inflammation from foods.
It’s possible to test for IgG food sensitivities with blood tests, but it’s unclear whether the results are accurate or clinically useful (see below).
Food reactions can also be caused by your body’s inability to break down parts of the food. This is called a food intolerance.
Symptoms of food intolerance can also cause digestive and non-digestive symptoms, including gas, bloating, diarrhea, constipation, rashes, headaches, joint pain, or brain fog.
Lactose intolerance is an example of a food intolerance. If you are deficient in the enzyme lactase, you may get gas and bloating from eating the lactose in dairy products. Other examples include FODMAP intolerance, histamine intolerance, sulfur intolerance, or salicylate intolerance.
There generally aren’t lab tests to identify food intolerances.
Types of Food Allergy Testing Kits
There are many types of food allergy test kits on the market intended to help you take the guesswork out of your food reactions. Some kits can be ordered online and completed at home, while others require a doctor’s office visit or blood draw.
Companies typically test different groups of foods, including meats, legumes, grains, dairy products, herbs and spices, nuts and seeds, and food additives to check for reactions. Most of these tests, like the popular EverlyWell test, look for IgG reactivity to foods.
Here’s a summary of the different types of test kits.
IgG food sensitivity tests: These usually use a blood sample to check for IgG antibodies to broad panels of common food allergens. Some kits are a finger prick home test, while others require a laboratory blood test.
Mediator release tests: These tests expose a blood sample to allergens and check for a non-specific cellular immune response in the blood sample. These tests require a blood draw.
Hair analysis tests: These tests use a hair sample and a “bio-resonance” machine to evaluate food sensitivities. Hair test kits are completed at home.
Stool tests: Some stool tests include markers for food reactivity to gluten, dairy, or other foods. Stool tests are completed at home.
Skin prick tests: These tests are usually completed by a healthcare provider or an allergist. Your skin is pricked with small needles that have allergens on them, such as pollen, shellfish, or pet dander. If your skin has a reaction, you are considered allergic to that item.
What Do Food Allergy and Food Sensitivity Test Results Tell You?
Food allergy testing kit manufacturers claim that their test results will tell you which foods you are intolerant to so you can remove them from your diet. But are these claims true?
According to a 2014 review paper on food sensitivity testing, none of the food testing methods, including IgG testing, mediator release testing, or hair analysis are scientifically validated . To quote:
The most helpful diagnostic test for food intolerance is food exclusion to achieve symptom improvement followed by gradual food reintroduction.
In other words, studies haven’t shown that patients’ symptoms improved from removing foods the test identified as reactive. (The one exception is skin prick tests conducted by an allergist ).
Some limited data supports the idea that IgG food sensitivity tests can provide better diet guidance, especially for IBS  and migraine patients [7, 8] than a placebo. Another study suggested that measuring antibodies against foods may improve the diagnosis of food allergy . However, IgG testing is not comprehensive because not all types of food reactions raise IgG antibodies.
At best, food allergy testing gives you a partial picture of your sensitivities, and at worst, doesn’t tell you very much at all.
The True Food Allergy Test: An Elimination Diet
Diagnosing food sensitivities and intolerances is also challenging because symptoms sometimes happen hours to days after ingestion , and they vary so widely . So, if testing isn’t reliable, what’s the best approach to identifying food triggers?
Two recent literature reviews concluded that the most useful diagnostic test for identifying food allergies and intolerances is an elimination diet [4, 11]. A 2019 literature review suggested the same, specifically for suspected FODMAP, wheat, and histamine intolerance .
Lack of reliable diagnostic biomarkers for all food intolerances result in an inability to target specific foods in the individual… a trial-and-error approach is used, whereby suspected food are reduced for a short-period and then re-challenged to assess response.
Elimination diets, such as the paleo diet or the low FODMAP diet, remove the most common inflammatory foods that frequently cause food symptoms. Eliminating common food allergens from your diet can:
Quickly calm down inflammation
Help you identify your trigger foods
Improve your digestive and non-digestive symptoms
Assuming the foods you eliminate are triggering your symptoms, you should start to feel better 2-4 weeks after removing them from your diet. Gradually reintroducing foods and monitoring symptoms can help you pinpoint which foods are triggering symptoms.
One of the biggest risks of inaccurate food allergy tests is an inappropriate use of elimination diets. Patients often drastically change their diet in response to their test results, leading to severely restricted diets and fear of food.
It’s vitally important to use elimination diets properly by systematically testing for food reactions and only continuing dietary changes that benefit you.
Let’s talk about how to properly do an elimination diet to test yourself for food intolerances.
How To Do an Elimination Diet
An elimination diet has three phases:
During the elimination phase, you remove foods that commonly contribute to food allergies, sensitivities, and intolerances. The most frequent culprits are gluten, dairy, soy, eggs, sugar, and processed foods. The paleo diet is an elimination diet that removes these foods.
After you reach a plateau of symptom improvement, you begin the reintroduction phase, reintroducing foods you removed to test for reactions. Typically, food reintroduction involves adding one food or food group in over the course of three days. If you react, continue to keep that food out of your diet, even after the elimination diet ends. If you don’t experience a reaction, you can safely add that food back into your diet.
During the maintenance phase, you continue to avoid the foods that cause symptoms and continue eating foods that don’t. Remember that multiple food intolerances are often a symptom of a greater immune dysregulation so while food elimination is helpful for symptom management, you will want to continue to look for underlying causes of food intolerance. This may help you to overcome food intolerances and build back the diversity of the diet.
It’s important to remember that no elimination diet is intended for long-term use. If you don’t notice any improvement on an elimination diet after 3-4 weeks, you can stop the diet and try a different approach.
Elimination Diet Options
Two elimination diets to improve food reactions are the Paleo diet and the low FODMAP diet. Choose the Paleo diet if you also struggle with cardiovascular concerns, extra weight, or diabetes.
Choose the low FODMAP diet if you primarily struggle with digestive symptoms or diagnoses, like IBS, IBD, bloating, diarrhea, or constipation.
If this basic elimination diet doesn’t help, more specific elimination diet options may be considered. If you have an autoimmune diagnosis, explore the autoimmune paleo diet (AIP). If your symptoms are more like allergies, with hives, itching, watery eyes, or runny nose, a low histamine diet may be the right option to help you get control over your symptoms.
Rebalancing your gut bacteria with probiotics has shown some promise for improving food intolerances, particularly lactose intolerance  and non-celiac gluten sensitivity [13, 14]. There is also some limited evidence that probiotics can help allergies and immune conditions, like histamine intolerance [15,16, 17].
Probiotics may have this effect because they help repair the gut dysbiosis that can contribute to food sensitivities [18, 19, 20]. It’s also been suggested that leaky gut may be one reason for food sensitivities, and probiotics have been shown to improve leaky gut [21, 22, 23].
Food allergy test kits aren’t likely to tell you what you should and shouldn’t eat with any degree of accuracy. A much better approach is to complete a 3-4 week elimination diet and food reintroductions to pinpoint your food sensitivities. If that doesn’t work, consider working with our clinic team to troubleshoot what else may be going on.
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