Should You Take a Food Sensitivity Test?

If you've ever experienced bloating, gas, stomach pain or other digestive discomfort after eating, you might wonder whether something you ate is to blame. You've tried cutting out different foods — milk, cheese, dairy, even coffee — but nothing seems to help.

The possibilities can seem endless, and the uncertainty might have you considering food sensitivity testing.

"Many people with irritable bowel syndrome (IBS) feel as though their symptoms are tied to what they eat," says Dr. Eamonn Quigley, a gastroenterologist at Houston Methodist. "Either they notice symptoms after most meals, or they are suspicious about a specific food they regularly consume."

But how do you know if your problems are related to a food sensitivity? And are the tests available really accurate? Dr. Quigley answers these questions and more.

Food sensitivity vs. food allergy: what's the difference?

One important clarification: a food allergy and a food sensitivity are very distinct issues, with different symptoms and potential complications. This is important to note since the term "food allergy" often gets used improperly.

Food allergies are mild to severe reactions to a specific food item, such as peanuts, tree nuts, seafood or shellfish.

"These reactions can be life-threatening — a person can go into anaphylactic shock if the allergy is severe," warns Dr. Quigley. "Food allergies are driven by IgE (Immunoglobulin E) antibodies and cause reactions that occur fairly immediately upon ingesting the offending food item."

Immunoglobulins, or antibodies, are proteins your immune system makes to help rid your body of things that shouldn't be there. There are different types, each with a specific role. IgE is involved in allergic reactions — it triggers your body's response to allergens like pollen or pet dander, sometimes leading to symptoms like sneezing or hives.

Food allergy symptoms include:

• Swelling of your tongue, lips, face or throat
• A tingling sensation inside your mouth
• Raised, itchy, red welts on your skin (hives)
• Throat constriction
• Anaphylaxis (hives, flushed or pale skin, heavy wheezing or shortness of breath, heart palpitations, feeling dizzy or lightheaded, nausea and vomiting)

If you have a food allergy, it's very important to know the signs and symptoms of anaphylaxis and seek immediate medical attention as soon as you suspect it.

"Food sensitivities or intolerances, on the other hand, are much less dramatic, though they can still lead to abdominal discomfort — which can be frequent if the person isn't sure what is causing the problem," explains Dr. Quigley. "These reactions aren't as immediate as food allergies, and they're also not mediated by IgE antibodies."

Food sensitivity symptoms can include:

• Excessive gas
• Bloating
• Belly pain
• Constipation and/or diarrhea

The most common underlying cause of food sensitivity is irritable bowel syndrome (IBS), with Crohn's disease and ulcerative colitis (which are collectively called inflammatory bowel disease, or IBD) and celiac disease being less common culprits. (Related: IBS vs. IBD: What's the Difference?)

What is food sensitivity testing?

So how do you know if you're intolerant to a certain type of food? That's where at-home food sensitivity testing comes in. There are many commercially available options these days, though most carry a hefty price tag.

The tests themselves are fairly simple. You receive a kit in the mail, do a small finger prick to collect a blood sample and then mail the kit in for analysis. Results are then shared in a report, with popular options flagging foods you may be reactive to.

Unlike allergy testing, which uses IgE antibody levels to measure specific and immediate reactions, food sensitivity testing measures IgG antibodies, which may or may not indicate a true food issue.

"IgG antibodies are associated with more prolonged immune reactions," says Dr. Quigley. "Using these antibodies to measure the response to various foods takes a lot of specificity and validation."

The bottom line: Buyer beware. Not all of the at-home food sensitivity tests are created equal. Dr. Quigley points out that the best way to start is by asking your gastroenterologist for help. They can explain the advantages and limitations of these tests, as well as which are the most well-validated.

"There is really only one food sensitivity test out there that has been clinically validated, and we are now starting to prescribe to patients," adds Dr. Quigley. "Results are shared with both the patient and their doctor, and we work together to determine whether dietary changes should be made — that's not a step that we recommend the patient do alone."

Are food sensitivity tests accurate?

Food sensitivity testing has been around for decades, and its reliability has been in question for the majority of that time. "It all started with IgE antibody testing in people with IBS, but that was never very useful — which we now know makes sense given that these are sensitivities, not food allergies."

Eventually, IgG antibodies were explored. While some early studies suggested that eliminating IgG-reactive foods could improve IBS symptoms, they faced criticism for being small and not well-designed. "Many lacked control diets, for instance," adds Dr. Quigley. "So these studies were dismissed for a long time."

A recent study, however, has reignited interest in food sensitivity testing, especially among experts in the field. More than 200 people with IBS were given either a diet based on food sensitivity test results or a placebo diet. The study's results showed improvement in symptoms for participants on the tailored diet, particularly in those with IBS-C (constipation type) and IBS-M (mixed type). The most commonly flagged foods? "Eggs, cow's milk and wheat were reported most often," adds Dr. Quigley.

He goes on to say, "While more research will be needed to confirm the findings of this new test, the early data is very promising for people with IBS," says Dr. Quigley.

Who should consider taking this new food sensitivity test?

If you have IBS, particularly if it's characterized by constipation (IBS-C) or the mixed symptoms (IBS-M), Dr. Quigley says the new food sensitivity test referenced above might be worth considering.

"This could be a really important intervention for people with IBS-M, in particular," Dr. Quigley adds. "Unlike with IBS-D (diarrhea type) and IBS-C, we haven't had good treatments available for people with IBS-M, and this new test gives us a way to potentially target their condition through diet modification to help reduce symptom severity."

Targeted diet changes will be welcome news for anyone who has tried and failed to keep up with the classic dietary interventions, like the FODMAP diet. That said, food sensitivity testing isn't a magic bullet.

"Is it going to cure someone's IBS? No," says Dr. Quigley. "But could it help some people? Yes. Managing IBS often requires multiple lifestyle changes, even medications in some cases, so this test could be yet another piece to the treatment puzzle." (Related: Irritable Bowel Syndrome Self-Care: 5 Ways to Take Control of IBS)

If you're struggling with digestive symptoms and suspect that food might play a role, talk to your gastroenterologist about whether a food sensitivity test makes sense for you. While the science is still evolving, your gastroenterologist can recommend a test that's clinically validated and consult with you afterward about how to take action on your results.