How to Test for Food Sensitivities

Written By: Jillian Foglesong Stabile MD, FAAFP, DABOM

Bloating, fatigue, indigestion, nausea, brain fog, and joint pain are among the many symptoms that can be associated with food sensitivities. If you’re experiencing these symptoms or others, you may be wondering how to test for food sensitivities. Fortunately, you have many choices for food sensitivity testing. This at-home testing guide will walk you through the process.

Understanding Food Sensitivities

Food sensitivities can have many symptoms. Some of these include [1,2]:

• Bloating
• Gas
• Abdominal pain
• Diarrhea
• Heartburn
• Nausea
• Headaches
• Upset stomach
• Vomiting
• Joint pain
• Brain fog
• Upper respiratory symptoms

These symptoms are common with other medical conditions such as celiac disease, hypothyroidism, irritable bowel disease, and inflammatory bowel disease. Food sensitivity testing is one option to help sort out whether your symptoms are due to sensitivities or other medical conditions.

Some food sensitivities are related to the foods themselves or additives in food. Others, such as lactose intolerance, can result from a lack of enzymes to break down food products. [2] Food sensitivity symptoms are usually associated with the amount of food you consume. If only small amounts of food are eaten, you may not experience any symptoms. Food sensitivity symptoms typically start within a few hours of eating the foods to which you are sensitive.

Food sensitivities are different from food allergies. Food allergies cause an immune system reaction and are generally more severe than sensitivities. They occur more quickly after exposure to a particular food and can be life-threatening in some cases.[3,4] Food allergies are generally mediated by immunoglobulin E, while food intolerances are often mediated by immunoglobulin G. [5]

Methods to Test for Food Sensitivities

There are two primary food sensitivity testing methods.

1. Obtaining a blood sample and looking for immunoglobulin G (IgG) levels for certain foods. IgG is a delayed immune response which may indicate that your body is viewing that food as a threat and responding to it. This is different than the immediate Immunoglobulin E (IgE) response associated with food allergies.[6]
2. Begin an elimination diet. Elimination diets involve removing foods of concern from your diet for several weeks to months and then adding them back to your diet to determine whether they cause you symptoms. There are many foods that you may choose to remove from your diet as part of an elimination diet. [7] Foods that commonly cause food sensitivities include, but aren’t limited to: wheat, dairy products, eggs, fish and other seafood, nuts, soy, corn, alcohol, sulfites, MSG, and more.

Keeping a food journal may help you identify food triggers that could be causing your symptoms and guide you in determining which foods to consider eliminating. Make sure to consult with your healthcare provider before starting an elimination diet to avoid nutritional deficiencies or exacerbating underlying medical conditions.

How At-Home Food Sensitivity Testing Works

In many cases, food sensitivity tests can be done from the comfort of your home. For at-home food sensitivity tests, you’ll order the test from the lab of your choice. Food sensitivity testing can vary based on the number of foods tested. Everlywell, for example, offers a Food Sensitivity Test that evaluates 96 common foods, or a Food Sensitivity Comprehensive Test that evaluates 204 foods.

Once you receive your kit, you’ll go online to register it. After that, you’ll follow the instructions provided with your kit to collect a blood sample. Some kits may require you to go to a lab to have blood drawn in a vial, but most can be completed with a finger prick and blotting blood on the provided test card. You’ll then mail your kit back to the lab and wait for your results. Most labs provide results within a few days of receiving your sample.

How to Prepare for a Food Sensitivity Test to Ensure Accurate Results

Proper preparation for a food sensitivity test is crucial to ensure that the results are as accurate and reflective of your body's true reactions as possible. If you want to get reactive results—meaning accurate IgG responses to the foods you're testing for—there are a few important steps to follow to make sure you’re setting yourself up for success.

1. Continue Eating the Foods You Suspect Are Problematic

One of the key factors in ensuring that you get reactive results is continuing to eat the foods you're testing for before you take the test. If you eliminate foods from your diet too soon, your body may no longer produce the IgG antibodies needed for the test, leading to falsely negative results. Here’s what to do:

• Avoid eliminating foods before testing. For example, if you suspect dairy or gluten may be a trigger, continue eating them regularly in the weeks leading up to your test.
• Consume a variety of foods that you think may be causing symptoms. If you're unsure which foods to include, try to stick to a varied diet that includes the top allergens like dairy, gluten, eggs, nuts, soy, and others.

2. Time Frame: Continue Eating Suspected Foods for 2-4 Weeks Before Testing

For the most accurate results, it’s important to eat the foods you're concerned about for 2 to 4 weeks before you take the test. This allows your body to produce IgG antibodies in response to the foods, which is crucial for detecting sensitivities. If you cut out certain foods too early, your test may not show the full picture of your sensitivities.

• For accurate results, continue consuming potential triggers for at least 2-4 weeks before testing.

3. Avoid Restrictive Diets or Detoxes

While it's tempting to try a detox or restrictive diet in the weeks before testing to "cleanse" your body, doing so could interfere with your test results. Detoxing or restricting food can mask sensitivities by reducing exposure to the foods that may be causing reactions.

• Don’t follow a restrictive or detox diet in the weeks leading up to your test.

4. Consider Your Medications and Supplements

Certain medications and supplements can affect the immune response and potentially interfere with test results, particularly if they suppress the immune system. Some medications, like steroids, can reduce inflammation or the immune system's ability to produce IgG antibodies, leading to false negative results.

• Steroids or immune-suppressing medications (e.g., corticosteroids, chemotherapy drugs)
• Antibiotics or probiotics (which can affect gut flora and immune responses)
• Anti-inflammatory medications (NSAIDs)

If you’re taking any of these medications or supplements, consult your healthcare provider to see if you should pause them temporarily before the test. Make sure to follow your healthcare provider’s guidance about when and how to stop these medications to get accurate results.

5. Maintain a Balanced Diet in the Days Leading Up to the Test

You don’t need to do anything special in the days leading up to the test. Just continue eating a balanced, regular diet, including all the foods you’ve been consuming regularly. Avoid fasting or altering your diet too drastically just before the test, as doing so may skew results.

• Eat normally: There’s no need to change your diet drastically before the test.
• No fasting required: Unlike some tests that require fasting, food sensitivity tests can usually be done without the need for any fasting.

6. Be Consistent with the Amount of Food You’re Consuming

The amount of food you consume is also important for ensuring accurate results. Moderate and consistent exposure is key, as eating large amounts of a suspected food intermittently may lead to skewed results.

• Eat moderate amounts of suspected foods consistently in the weeks leading up to the test.

7. Pay Attention to the Timing of the Test Relative to Your Symptoms

While food sensitivity tests can detect an immune response to foods, symptoms may not always be present when the test is conducted, especially if you’ve recently consumed the food or haven't eaten it for a while.

• If possible, take the test after you've had some symptoms, but ideally, not when they’re at their worst.
• Record your symptoms in a journal to identify patterns and make sure you’re not missing any potential food triggers.

8. Follow the Test Kit Instructions Carefully

Once you receive your at-home food sensitivity test kit, make sure to follow the instructions provided carefully. Each test may have different instructions for collecting your sample, whether it’s a blood sample via finger prick or saliva.

• Register your kit online as soon as you receive it.
• Carefully read the instructions on how to collect the blood sample. Most tests involve pricking your finger and applying a few drops of blood to a test card, but some tests may require sending your sample to a lab.
• Return your sample promptly to avoid any delays in the testing process.

How to Interpret Your Food Sensitivity Test Results

When you receive your test results, you may be wondering how to interpret them. Your test results will usually be reported as an IgG level graded from no reactivity to high reactivity. [6] The level of IgG roughly corresponds to the immune response to the food tested. However, it’s important to understand that IgG levels, regardless of how high they may be, do not necessarily correspond with the degree of symptoms you experience when you consume a particular food. For this reason, food sensitivity testing is usually recommended in combination with an elimination diet. Food sensitivity testing is just the first step in determining how much food sensitivities are responsible for your symptoms.

Understanding IgG Test Results

IgG (Immunoglobulin G) testing measures the immune system's delayed response to specific foods. These results are typically presented with a numerical scale or a range that shows how reactive your immune system is to various foods. The IgG levels correlate with how much antibody your body produces in response to a specific food.

Common IgG Result Ranges:

• No Reactivity: This indicates that your body is not producing a significant immune response to a particular food. Essentially, your immune system is not seeing the food as a "threat."
• Low Reactivity: This suggests a mild response to a food. It doesn’t necessarily mean you will experience symptoms, but it’s worth keeping an eye on.
• Moderate Reactivity: A moderate response means that your immune system has been activated by this food, and you may experience mild to moderate symptoms. It may be beneficial to eliminate this food and monitor changes.
• High Reactivity: High reactivity signifies a significant immune response, suggesting that this food may be a major trigger for your symptoms. It's highly recommended to avoid this food and consult a healthcare provider for further guidance.

Example of Test Result Breakdown:

• Food: Gluten
  Result: Moderate Reactivity
  Interpretation: The body has shown a moderate immune response to gluten. If you experience symptoms like bloating, fatigue, or headaches after eating gluten, this result suggests gluten could be a potential trigger.
• Food: Dairy
  Result: High Reactivity
  Interpretation: The test indicates a significant reaction to dairy, which is likely contributing to your digestive issues or other symptoms. Eliminating dairy may reduce symptoms.

Correlation Between IgG Levels and Symptoms

It’s important to understand that IgG test results don’t always directly correlate with the intensity of symptoms. Just because a food has a high IgG level doesn’t mean you will always experience severe symptoms when you eat it. Similarly, a food with a low IgG response doesn’t guarantee that it’s not affecting your health in subtler ways.

• Food Sensitivity is Often Dose-Dependent: Eating a small amount of a food might not trigger symptoms, but larger portions may.
• Multiple Food Sensitivities: You may have sensitivities to several foods at once, possibly compounding chronic symptoms like fatigue, headaches, or digestive discomfort.

Cross-Reactivity in Test Results

Some foods with similar proteins may cause cross-reactivity, meaning your immune system reacts to foods that are similar to the ones you are sensitive to. For instance:

Example: If you are sensitive to cow's milk, you might also experience mild reactions to goat’s milk or sheep’s milk due to similar protein structures.

This is why it's essential to follow up with an elimination diet, especially if you have high IgG reactivity to multiple foods in the same category (e.g., all dairy-related foods).

Steps to Take After Testing for Food Sensitivities

So you’ve taken the food sensitivity test and have your results; what now? The next step after a food sensitivity test is an elimination diet. You can use the result of your food sensitivity testing to guide your elimination diet. This will help you determine if the foods that are showing an IgG immune reaction are causing your food sensitivity symptoms. After consultation with your healthcare provider, you may want to eliminate the foods that cause an IgG response and then reintroduce them after a few weeks or months while monitoring your symptoms.

Results Are a Starting Point, Not a Final Diagnosis

IgG testing is a useful tool, but it should not be used as the sole basis for diagnosing food sensitivities. Results should be interpreted alongside:

• Your Symptoms: Track your symptoms and compare them to the foods that show up in the test results.
• Clinical Evaluation: Work with a healthcare provider to confirm your results and rule out other potential causes.
• Elimination Diet: Use the test results to guide your elimination diet. Removing high-reactivity foods and reintroducing them can clarify which ones truly cause problems.

When to Consult a Healthcare Professional

Symptoms of food sensitivity can be similar to symptoms of other health conditions. If your symptoms are severe or persistent, you should consult with a healthcare professional rather than relying on at-home testing.

Other signs or symptoms that indicate that you need immediate medical attention include [1]:

• Unexplained weight loss
• Severe abdominal pain
• Severe nausea, vomiting, or diarrhea
• Reactions to food such as rash, swelling, or trouble bleeding
• Bloody stools

Your healthcare provider may want to rule out conditions such as inflammatory bowel diseases, irritable bowel syndrome, or other health conditions with symptoms that can mimic those of food sensitivity.

Learn More About Your Digestive Health and Food Sensitivities With Everlywell

Food intolerance can cause distress and decrease your quality of life. At Everlywell, we offer a variety of lab tests and virtual care services that can help you take control of your health and better understand your body.

If you’re looking to learn more about how your body reacts to certain foods, consider using an at-home Food Sensitivity Test from Everlywell. Our food sensitivity test evaluates your body’s IgG response to 96 common foods. For even more information, you can take the Food Sensitivity Comprehensive Test that evaluates 204 foods. If you have questions about the next step for managing food sensitivity or any other health concerns, you can schedule an online visit with one of our certified healthcare professionals.

References

1. Food intolerance. Cleveland Clinic. Last Reviewed August 11, 2021. Accessed December 23, 2024. Medical Citation URL.
2. Website N. Food intolerance. nhs.uk. Last Reviewed November 25, 2022. Accessed December 23, 2024. Medical Citation URL.
3. Food Intolerance defined. American Academy of Allergy Asthma and Immunology. Last Reviewed July 8, 2024. Accessed December 24, 2024. Medical Citation URL.
4. Food Allergies | Causes, symptoms & treatment | ACAAI Public website. ACAAI Patient. Last Reviewed June 28, 2023. Accessed December 24, 2024. Medical Citation URL.
5. Causes and prevention of food allergy. NIAID: National Institute of Allergy and Infectious Diseases. Last Reviewed June 10, 2024. Accessed December 24, 2024. Medical Citation URL.
6. Lavine E. Blood testing for sensitivity, allergy or intolerance to food. Canadian Medical Association Journal. 2012;184(6):666-668. Medical Citation URL.
7. Clinic C. Why and How To Start an Elimination Diet. Cleveland Clinic. Published April 12, 2022. Accessed December 24, 2024. Medical Citation URL.
8. Geiselman JF. The Clinical Use of IgG Food Sensitivity Testing with Migraine Headache Patients: a Literature Review. Current Pain and Headache Reports. 2019;23(11). Medical Citation URL.
9. Caminero A, Meisel M, Jabri B, Verdu EF. Mechanisms by which gut microorganisms influence food sensitivities. Nature Reviews Gastroenterology & Hepatology. 2018;16(1):7-18. Medical Citation URL.
10. The myth of IgG food panel testing | AAAAI. Medical Citation URL.
11. Hunter JO. Food elimination in IBS: the case for IgG testing remains doubtful. Published August 1, 2005. Medical Citation URL.
12. Physicians say tests for food intolerance aren't supported by science - American College of Gastroenterology. American College of Gastroenterology. Published April 13, 2012. Medical Citation URL.
13. Everlywell. Things to know before I test for Food Sensitivity. Everlywell Knowledge Base. Published April 12, 2024. Accessed December 17, 2024. Medical Citation URL.