Definition and Overview

Food intolerance is a common problem. It affects thousands of people around the world. It causes symptoms when a person eats certain foods that his or her body cannot properly digest. It is different from food allergy because it does not trigger an immune response.

Food intolerance is a mild condition. People who have it have nothing to worry about because it does not lead to serious illnesses. Its symptoms are limited to digestive problems. Food allergy, on the other hand, can be severe. In some cases, it is even fatal. In the United States, about 20,000 people require emergency medical care for allergic reactions to food every year.

Anaphylaxis, a severe food allergic reaction, kills about 200 people each year in the United States.

Also, unlike food intolerance, food allergy can trigger symptoms even when a person eats only a small amount of food that he or she is allergic to.

Food intolerance does not require treatment. It resolves on its own within hours. Its symptoms go away completely when the person stops eating the food that his or her body cannot digest.

Causes of Condition

What causes food intolerance to occur is not fully understood. In many cases, it occurs because a person does not have an enzyme that the body needs to digest certain foods properly. For example, people who cannot tolerate dairy products lack lactase. Lactase is the enzyme that the body needs to digest milk sugar. Food intolerance can also be caused by defects that affect transporter molecules. These include those that transport sugar from fruits and carbohydrates. Undigested foods end up in the large intestines. This triggers bacterial overgrowth and excessive fermentation. As a result, patients develop symptoms. The most common are bloating and diarrhoea.

The risk of this condition is higher in people who have undergone bowel resection. This is because they may have a higher than average risk of bacterial overgrowth in their digestive system.

Key Symptoms

Signs of food intolerance are bloating and diarrhoea as well as flatulence and stomachache. Some patients also have a cough and runny nose. Other people present with hives. These symptoms can show several hours after the offending food is eaten. This is in contrast with food allergy in which the person almost always develops the symptoms right away.

Who to See and Types of Treatments Available

A person with food intolerance does not have to see a doctor. This is because they do not need any form of treatment. Their symptoms would go away after a few hours. They can prevent the symptoms from recurring by removing the offending food from their diet.

However, some people cannot figure out what food their body cannot tolerate. To know what food to avoid, patients can keep a list of everything they eat. They can then remove one food from their diet at a time. They will need to wait up to two weeks to see if they develop any symptoms. They have to do this until their symptoms go away and never come back.

Common foods that many people cannot digest are dairy products and chocolates as well as eggs and food additives. The list also includes strawberries and tomatoes as well as citrus fruits and wine.

If a person does not want to wait for weeks to get results, he or she can go to a doctor for a skin prick test. In this procedure, the skin on the forearm or back is pricked. A small amount of food or allergen solution is then placed on the skin. The doctor will then wait until the substances are absorbed by the skin. A person with food intolerance will develop a raised bump on the site during the test.


  • Food intolerance. National Health Service.

  • Guidelines for the diagnosis and management of food allergy in the United States: Summary for patients, families and caregivers. National Institute of Allergy and Infectious Diseases.

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