Could You Have a Food Intolerance?

Reviewed by Carol DerSarkissian on June 14, 2020


If you have a bad reaction to a certain food, it may be an allergy or it could be a food intolerance. An intolerance means your body has a hard time digesting a food or an ingredient in it, such as a dye or a chemical.

That's different from an allergy. An allergy is when your body's immune system thinks the food is harmful and tries to fight it off.


Common Symptoms of Food Intolerance

Some symptoms of food intolerance -- sometimes called sensitivity -- and allergies are similar. You should see a doctor to learn for sure what's causing your problem, but there are some clues.

Intolerances usually show up as stomach trouble like gas, pain, bloating, or diarrhea -- not the rashes, hives, and watery eyes that are common with allergies.

You often have to eat a lot of the food, and it may take an hour or more for you to have symptoms. It can be uncomfortable, but food intolerances usually aren't dangerous.


Common Problems

Intolerances are often linked to things in the food, such as:

  • Lactose, a natural sugar found in milk, cheese, and other dairy products
  • Sulfites, for instance in wines, pickled foods, and sodas
  • Gluten, a protein in wheat, barley, rye, and some other grains
  • Fructose, a natural sugar found in most fruits and also in high-fructose corn syrup, a sweetener used in some soft drinks and some processed foods, like pastries and cereal
  • FODMAPs (fermentable oligosaccharides disaccharides monosaccharides and polyols), carbohydrates that draw water into your intestine during digestion

FODMAPs cause gas, bloating, and abdominal pain in some people (usually those with other digestive issues). Many plant foods contain FODMAPs, including apples, honey, garlic, and wheat.


Tests and Treatment

Your doctor will ask about your medical history, the foods you eat, and your symptoms and may suggest some screening tests. You also may need to keep a detailed food and symptoms diary.

Your doctor may suggest an exclusion diet: You'll stop eating foods that are the most common intolerance triggers. As these foods are slowly brought back into your eating plan, you and your care provider will keep track of your symptoms so you can see which foods or additives you are sensitive to.


Lactose intolerance is very common in adults. To see if you have it, your doctor may ask you to take dairy out of your diet for a couple of weeks to see if you feel better.

Your doctor also may recommend a test called a hydrogen breath test, which you can take at their office. Depending on what they think your intolerance might be, they'll give you a drink with large amounts of lactose, fructose, sucrose, or glucose. They'll then test your breath every 15 minutes to check the amount of hydrogen or methane. If you have too much of one of these, it indicates your body isn't able to break it down. That likely means you have an intolerance. For this test to work the way it should, you may need to eat a low-carb diet for a few weeks before testing.

Prevention for food intolerances is much the same as for allergies: Read labels and be careful when eating out to avoid the food or ingredient as much as possible.

WebMD Medical Reference



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American Academy of Allergy Asthma and Immunology: "Food Allergy Overview," "Food Allergy."

Asthma and Allergy Foundation of America: "Food Intolerance."

Canadian Digestive Health Foundation: "Understanding FODMAPs."

Fedewa, A. and Rao, S.S.C, "Dietary fructose intolerance, fructan intolerance and FODMAPs."

Food and Drug Administration: "High Fructose Corn Syrup: Questions and Answers."

National Health Service (UK): "Diagnosing lactose intolerance."

National Institute of Allergy and Infectious Diseases: "Food Allergy: An Overview."

UpToDate: "Patient information: Food allergy symptoms and diagnosis (Beyond the Basics)."

University of Michigan Health System: "Hydrogen Breath Test."

Food Allergy Research & Education: "Facts and Statistics."

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