How Do Food Intolerance Tests Work? Understanding Types, Accuracy, and Results
Written By: Jillian Foglesong Stabile, MD, FAAFP
Types of Food Intolerance Tests
A food intolerance, also known as a food sensitivity, means that your digestive tract is having a hard time breaking down a specific type of food.[1] Food intolerances can cause significant distress and discomfort. This may be due to problems with digestive enzymes or components of the food.[2]There are several ways to test for food intolerance, with the most common tests being breath testing, diet tracking and elimination, and blood tests.
Breath Testing
Breath testing is used most commonly in lactose intolerance. With this test, you drink something with lactose and then breathe into a bag several times over a few hours. If you have lactose intolerance, you will build up hydrogen in your breath, which can be detected.[4]
Diet Tracking and The Elimination Diet
An elimination diet allows you to identify how your body responds to different foods.[5] With an elimination diet, you remove certain foods from your diet for a period of time, usually weeks to months, and then gradually introduce them back to your diet to see how they affect you. Some of the common foods that people will eliminate as part of an elimination diet include[6]:
- Dairy
- Eggs
- Fish
- Wheat
- Soy
- Shellfish
- Nuts
- Alcohol
- Corn
- Gluten
- Fish
- Fructose
- Monosodium glutamate (MSG)
- Sulfites
Before starting an elimination diet, it is important to talk with your healthcare provider to avoid exacerbating an underlying medical condition or ending up with nutritional deficiency. Many times, an elimination diet may start with a food journal. A food journal helps you track what you are eating and the symptoms you are experiencing, allowing you to identify foods that may be contributing to your symptoms.
IgG Blood Tests
Blood testing is also available to test for food intolerances. Blood testing for food intolerances measures the amount of immunoglobulin G (IgG) specific to certain food components in your blood.[7] IgG is a type of antibody that triggers a delayed immune response (as opposed to an allergic reaction).[10] IgG levels can be measured specific to certain kinds of food. Elevated levels suggest that your body recognizes those foods as a threat and causes intolerance.
For this type of testing, there are two ways to obtain a sample, in a standard lab setting or in your home. For the lab setting, you go to a lab draw station. After you check in, you’ll sit in a chair, and a tourniquet will be applied. A needle will be introduced into a vein (usually in your arm), and blood will be removed into a vacuum tube. For in-home testing, you may be able to collect a sample with a finger stick. You dab the blood onto a card, which then gets mailed back to the lab for analysis.
Food intolerance blood testing can help guide you if you are considering an elimination diet. With a food intolerance test, you can identify foods to eliminate and shorten the time it takes to do the elimination diet.
How Accurate Is a Food Intolerance Test?
IgG testing for food intolerance is a somewhat controversial subject. Some studies have shown promise for food intolerance testing as a tool for healthcare providers with patients who have migraine symptoms.[9] Other evidence has shown questionable accuracy and clinical relevance for IgG-based food sensitivity testing. Many medical academies, such as the American Academy of Allergy, Asthma & Immunology, recommend against using IgG-based food intolerance testing.[10] One of the concerns that healthcare organizations express regarding IgG-based food intolerance testing is false-positive testing, and a number of studies have shown inconclusive results.[11] This is because the immune system may produce an IgG immune response to the presence of food, whether or not the food is actually causing symptoms of intolerance.[10]
This is why many companies like Everlywell that offer food intolerance testing recommend using the test as a guide for the two-part elimination diet, not necessarily depending on the test results by themselves.
What Foods Can a Food Intolerance Test Evaluate?
Many foods can be evaluated using a food intolerance test. Hydrogen breath testing is primarily used for lactose intolerance but may also be used for conditions such as small intestine bacterial overgrowth (SIBO). An elimination diet can be used to evaluate the body’s response to any food, though it is important to pay close attention to food labels as foods such as wheat and dairy are frequently included as fillers and ingredients in more foods than you may realize.
IgG-based testing can evaluate a number of different foods. For example, the Food Sensitivity Test from Everlywell tests for sensitivity to 96 common foods, while the Food Sensitivity Comprehensive Test from the same company evaluates for sensitivity to 204 different foods. Testing offered by other companies may include other foods.
How Can I Get Tested for Food Intolerance?
Many people seek care from specialists such as a gastroenterologist for digestive health concerns. If you’re wondering if a gastroenterologist will test for food intolerance, the answer is that it probably depends. Because IgG-based food intolerance testing is not recommended by many traditional medicine academies, many healthcare providers may not offer food intolerance testing. The American College of Gastroenterology released a press statement discussing physician concerns about a lack of scientific rigor regarding food intolerance testing.[12]
Many people choose to seek this type of testing independently. Several online-based companies and labs offer testing that you can do from the comfort of your own home. Companies that offer at-home testing options, such as Everlywell, also offer consultations with a healthcare provider to help you choose the best test for your symptoms.
There are several signs and symptoms that may be a cause for concern and should prompt you to seek immediate medical attention rather than trying to learn more about your symptoms on your own. Some of these symptoms include[1]:
- Severe abdominal pain or diarrhea
- Bloody stool
- Severe reaction to food, including rash, swelling, or difficulty breathing
- Unexplained weight loss
You may want to consider consulting your healthcare provider to rule out medical conditions such as inflammatory bowel disease (Chron’s disease or ulcerative colitis), irritable bowel syndrome, or other medical causes of your symptoms, as many of these conditions have similar symptoms to food intolerance.
What Are the Symptoms of a Food Intolerance?
The symptoms of a food intolerance can vary from patient to patient and, in some cases, from food to food. Some of the symptoms of food intolerance include[1]:
- Pain in the abdomen
- Diarrhea or constipation
- Bloating and increased gas
- Heartburn or upset stomach
- Nausea and vomiting
- Headaches
Symptoms of a food intolerance usually start within a few hours of eating but can sometimes take days to appear. If you only consume a small amount of the food you are intolerant to, you may not have symptoms.
What Causes a Food Intolerance?
A food intolerance can be caused by a sensitivity to a chemical or additive in the food you eat, such as gluten, histamines, or caffeine. Food intolerance can also be caused by the absence of enzymes in the body to break down certain foods, such as the lactose found in dairy products. Lactose intolerance is the most common form of food intolerance and occurs when your body fails to produce the lactase enzyme that breaks down the lactose sugar present in dairy products.[3]
Anyone can develop a food intolerance, but certain types of medical conditions may increase your risk of food intolerance. Celiac and inflammatory bowel diseases, such as Chron’s disease and ulcerative colitis, can increase your risk of developing food intolerance.[1]
FAQS on Food Intolerance Testing
What is the difference between food intolerance and food allergy testing?
A food allergy activates the immune system rather than the digestive system. Food allergies are generally more severe than food intolerances. A food allergy may cause hives and other rashes, difficulty breathing, wheezing, and, in severe cases, anaphylaxis. Food allergies can be life-threatening if untreated.[2] In contrast, a food intolerance may cause significant discomfort and impact your quality of life, but it is unlikely to be life-threatening.
How long does it take to get the results from a food intolerance test?
Many labs can provide results within a week of receiving the test results.
Can I do a food intolerance test at home?
Yes, many companies, such as Everlywell, offer testing that you can collect from the comfort of your own home.
Learn More About Your Digestive Health With Everlywell
Food intolerance can cause significant distress and impact your day-to-day life. If you’re looking to learn more, consider visiting us at Everlywell. We offer a range of lab tests and virtual care services that can help you get to the bottom of your health concerns.
If you’re concerned or curious about your food intolerances, consider using an at-home Food Sensitivity Test from Everlywell. Our food sensitivity test evaluates your body’s IgG response to 96 common foods to help guide a two-part elimination diet. For even more information, you can take the Food Sensitivity Comprehensive Test, which evaluates 204 foods. If you have questions about your health, you can schedule an online visit with one of our certified healthcare professionals.
References
- Cleveland Clinic. Food intolerance. Last reviewed August 11, 2021. Accessed November 7, 2024. Medical Citation URL.
- American Academy of Allergy, Asthma & Immunology. Food intolerance defined. Last updated July 8, 2024. Accessed November 7, 2024. Medical Citation URL.
- NHS UK. Food intolerance. Last reviewed November 25, 2022. Accessed November 7, 2024. Medical Citation URL.
- Cleveland Clinic. Hydrogen breath test. Last reviewed May 3, 2022. Accessed November 7, 2024. Medical Citation URL.
- Sutherby R. How to use a food elimination diet to discover your food sensitivities. Everlywell. Updated April 11, 2024. Accessed November 7, 2024. Medical Citation URL.
- Cleveland Clinic. Why and how to start an elimination diet. Accessed November 7, 2024. Published April 12, 2022. Medical Citation URL.
- Lavine E. Blood testing for sensitivity, allergy or intolerance to food. CMAJ. 2012;184(6):666-668. doi:10.1503/cmaj.110026
- Everlywell. Food sensitivity testing: how it works – and how it can improve your well-being. Updated January 2, 2024. Accessed November 7, 2024. Medical Citation URL.
- Geiselman JF. The clinical use of IgG food sensitivity testing with migraine headache patients: a literature review. Curr Pain Headache Rep. 2019;23(11):79. doi:10.1007/s11916-019-0819-4
- American Academy of Allergy, Asthma & Immunology. The myth of IgG food panel testing. Updated January 2, 2024. Accessed November 7, 2024. Medical Citation URL.
- Hunter JO. Food elimination in IBS: the case for IgG testing remains doubtful. Gut. 2005;54(8):1203. Medical Citation URL.
- Sesol J. Doubts cast on food intolerance testing. Chicago Tribune. Updated November 3, 2021. Accessed November 7, 2024. Medical Citation URL.