Harvard Women's Health Watch

Food allergies and food intolerances

Both are on the rise — and it's important to know the difference.

It's no fun to live in fear of food. If you can't tolerate certain foods, you probably dread the gastrointestinal distress they can cause. If you have a food allergy, the stakes are higher: a meal could end in a trip to the emergency room. Or, like many people, you could be uncertain whether your symptoms are due to an allergy (which requires eliminating all traces of the food from your diet) or an intolerance (which can be managed with less drastic measures). An analysis revealed that while 13% of adults described themselves as allergic to peanuts, milk, eggs, fish, or shellfish, only 3% truly were. Other studies have shown that undetected food allergies may play a role in several medical conditions.

The prevalence of food allergies — or at least diagnosed food allergies — has increased steadily since the early 1990s; an estimated 5% of children and 4% of teens and adults are now affected. Food intolerance is harder to track, but estimates of its prevalence range from 2% to 20%. In December 2010, the National Institute of Allergy and Infectious Diseases (NIAID) published guidelines for the diagnosis and management of these conditions. The guidelines explain how to distinguish a food allergy, which can be fatal, from a food intolerance, which can cause a great deal of discomfort but rarely has serious health consequences. The difference: food allergies are orchestrated by the body's immune system; food intolerance results from an inability of the gut to digest food normally.

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