Stacey Colino

Is It a Food Allergy ... or Food Intolerance?


You hear it a lot: Someone has a bad reaction to a food and automatically thinks it's a food allergy. But the truth is it's more likely to be food intolerance.

"Food intolerances are relatively common, whereas true food allergies are relatively rare," says Dr. Andrew Smith, assistant professor of clinical medicine at the University of Cincinnati and allergy section chief at the Cincinnati VA Medical Center.

What's the difference?

Food Allergy: An Immune Response

When you have a food allergy, your immune system perceives a specific food as harmful and develops antibodies against it, explains Smith. When you eat the problematic food again, the antibodies attack the food, triggering the release of histamine and other chemicals that cause symptoms of an allergic reaction. "These reactions usually occur quickly -- within minutes to an hour -- when a relatively small amount of the food is eaten," says Smith.


Food allergies can cause rashes, hives, stomach pain, diarrhea, vomiting, shortness of breath, swelling of the lips, tongue or throat, or even chest pain. In some cases, such allergic reactions can be life-threatening.

Common culprits:

Milk, eggs, wheat, peanuts, tree nuts, soy, fish, shrimp and shellfish account for approximately 90 percent of allergic reactions to food, says Smith.

How it's diagnosed:

If your doctor suspects you have a food allergy, you'll probably be referred for allergy testing -- either skin-prick testing to elicit a reaction, or blood tests to identify allergic antibodies to specific foods.

Getting relief:

"At this time, there is no way to cure food allergies," says Smith, so the best course of action is to strictly avoid the foods that cause adverse reactions. If you have a severe food allergy, it's wise to carry antihistamines and an automatic epinephrine injection to treat symptoms, just in case you accidentally consume the food.

Food Intolerance: A Digestive Response

Unlike food allergies, which are triggered by the immune system, food intolerances begin in the digestive system. The mechanisms behind most food intolerances aren't as clearly understood as food allergies, with the exception of lactose intolerance.

If you have lactose intolerance, your body has trouble digesting lactose -- a natural sugar found in milk and dairy products -- because it doesn't produce enough of an enzyme called lactase, explains Dr. Cindy Yoshida, a gastroenterologist in Charlottesville, Va., and author of No More Digestive Problems. Symptoms typically start within two hours after eating lactose-containing foods and tend to be worse if a larger quantity is consumed.


Lactose intolerance typically causes diarrhea, abdominal pain, bloating and gas. Other food intolerances can also trigger nausea, vomiting, heartburn, fatigue or irritability, as well as non-specific symptoms, which makes it more difficult to figure out what the person is reacting to, says Yoshida. Food intolerances aren't life-threatening, but the discomfort can be considerable.

Common culprits:

Food intolerances can result from a wide range of foods, the most common of which are milk and dairy products, gluten (a naturally occurring protein found in wheat, barley and rye), and food additives such as MSG (monosodium glutamate) or sulfites.

How it's diagnosed:

To diagnose food intolerance, your doctor will rely primarily on your history of symptoms and the patterns you describe, so it's a good idea to keep a food diary to help identify connections between what you eat and your symptoms. There are also specific tests that can be done for lactose intolerance and gluten intolerance (aka celiac disease).

Getting relief:

Managing food intolerances generally involves limiting or avoiding problematic foods. In some cases, you may be able to consume small amounts, without paying the price. If you have lactose intolerance, you can also take lactase enzyme tablets to help you digest lactose.

So if your stomach is giving you trouble, schedule an appointment with your doctor. If you have food intolerance, figuring out the culprit is the first step in helping you feel better. And if it's a food allergy, pinpointing the offender just may save your life.


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Health - Is It a Food Allergy ... or Food Intolerance?