Standard Methods to Determine Food Allergies and Intolerances

Are you unsure if your IBS symptoms are a result of food allergies or food intolerances? Many people with IBS think they have food allergies, although it is more likely to be a food intolerance. Whether you have an allergy or an intolerance, there are several methods to test for both.

Food allergy tests

If you think you have an allergy, visiting an allergist can make all the difference. He’ll ask detailed questions about your symptoms and your family history of allergies and then determine which tests, if any, are needed.

There are a few common ways to test for allergies. A skin test is the most accurate method for testing. In this test, your skin is exposed to suspected allergens and is observed for allergic reactions.¹ A common, but less accurate, method of testing is a blood test. A blood test detects allergies by measuring IgE, allergy-related antibodies.¹ Skin prick tests are the gold standard but are not always possible. Skin tests may be contraindicated with certain health conditions or medications.¹ Avoid tests like hair analysis, applied kinesiology, facial thermography, and gastric juice analysis.¹

Although food allergies are less common than food intolerances in people with IBS, there are some benefits to getting an allergy test. An allergy test can identify other allergens you didn’t know of that are disrupting your life in other ways. For example, you may get a food allergy test because you believe you may be allergic to wheat, but you find out you are actually allergic to sesame seeds.

Food intolerance tests

Primary methods to identify food intolerances include food journaling and elimination diets. A food journal or diary should record exactly what was eaten (including serving size), any special or non-obvious ingredients, time of day in which it was eaten, and any symptoms experienced after.² For example, if you had yogurt for breakfast, you may log: 1/2 cup serving of low-fat vanilla yogurt with 1/4 cup granola, a handful of blueberries, and 10 almonds; felt bloated and abdominal pain one hour after consuming. A detailed food journal should be kept for at least two weeks.²

You can also work with a registered dietitian to implement and monitor an elimination diet. An elimination diet involves removing foods from your diet that you suspect you are sensitive to and is the primary approach used to remove FODMAP’s from one’s diet. There are four steps to an elimination diet:³

1. Planning: strategize and talk to your provider about which foods are causing you the most discomfort. Make a list of problem foods and keep a diary (similar to described above) to note how you feel after consuming such foods.
2. Eliminate: Remove the foods that are problematic for 2 to 3 weeks. You must eliminate the entire food, and there are no exceptions. This step can take a lot of discipline and effort. It is important to pay careful attention to food labels or ask for help when dining out.
3. Reintroduction: Slowly add the food back into your diet. Each food should be introduced individually over 2 to 3 days. During this phase, take note of any symptoms you feel. A food journal is also recommended during this phase.
4. Recreate a long-term diet plan: Based on your results, create a diet that works for you long-term. The diet should not include any foods that caused discomfort or pain over the past several weeks. Creating this new diet may take time and many trials.

There are still many unknowns on the relationship between food intolerances and IBS. Research has mainly focused on specific foods and their effects on the microbiome.⁴ An elimination diet can be an eye-opening experience and allow you to feel in control of your IBS symptoms! If you are interested in trying it out, you should consider consulting with a registered dietitian.