What's the difference between a food intolerance and a food allergy?

Answer From James T C Li, M.D., Ph.D.

Physical reactions to certain foods are common, but most are caused by a food intolerance rather than a food allergy. A food intolerance can cause some of the same signs and symptoms as a food allergy, so people often confuse the two.

A true food allergy affects the immune system. Even small amounts of the offending food can trigger a range of symptoms, which can be severe or life-threatening. In contrast, a food intolerance often affects only the digestive system and causes less serious symptoms.

If you have a food intolerance, you may be able to eat small amounts of the offending food without trouble. You may also be able to prevent a reaction. For example, if you have lactose intolerance, you may be able to drink lactose-free milk or take lactase enzyme pills (Lactaid) to aid digestion.

Causes of food intolerance include:

  • Absence of an enzyme needed to fully digest a food. Lactose intolerance is a common example.
  • Irritable bowel syndrome. This chronic condition can cause cramping, constipation and diarrhea.
  • Sensitivity to food additives. For example, sulfites used to preserve dried fruit, canned goods and wine can trigger asthma attacks in people who are sensitive to food additives.

What about celiac disease?

This chronic digestive condition is triggered by eating gluten, a protein found in wheat and other grains. Celiac disease has some features of a true food allergy because it involves the immune system. Symptoms often include gastrointestinal issues as well as those unrelated to the digestive system, such as joint pain and headaches. However, people with celiac disease are not at risk of anaphylaxis.

If you have a reaction after eating a particular food, see your doctor to determine whether you have a food intolerance or a food allergy.

If you have a food allergy, you may be at risk of a life-threatening allergic reaction (anaphylaxis) — even if past reactions have been mild. Learn how to recognize a severe allergic reaction and know what to do if one occurs. You may need to carry an emergency epinephrine shot (Adrenaclick, Auvi-Q, EpiPen) for emergency self-treatment.

If you have a food intolerance, your doctor may recommend steps to aid digestion of certain foods or to treat the underlying condition causing your reaction.

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April 21, 2022 See more Expert Answers