How 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.

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.

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.

When you receive your results, they will be graded on a reactivity scale — from no reactivity to high reactivity — reflecting your immune system's IgG response to each food tested. Keep in mind that IgG levels don't always directly correspond to symptom severity, and food sensitivity testing works best in combination with an elimination diet. For a full breakdown of how to read your results, see our guide to IgG food test results interpretation.

Food sensitivities can affect day-to-day comfort and make it more difficult to identify which foods work best for your body. Understanding your potential triggers may help you make more informed choices about your diet and overall wellness.

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 reactivity to 96 common foods, while the Food Sensitivity Comprehensive Test evaluates 204 foods. If you have questions about your results or next steps, you can also schedule an online visit with a certified healthcare provider.