01/08/2011 11:35 am ET | Updated May 25, 2011

Food Allergies: Your Questions, Answered

From celebrities shunning gluten to schools banning peanuts, food allergies are all over the news. To get up-to-the-minute info on why so many people are affected, Health went to one of the country's leading experts, Stephen I. Wasserman, M.D., a professor of medicine and researcher at the University of California, San Diego, and a fellow of the American Academy of Allergy, Asthma, and Immunology.

What's behind the increase in food allergies?
There are a lot of different theories. One is the hygiene hypothesis, which notes that because we're growing up in cleaner environments, our immune systems don't become properly educated and start overreacting to harmless things.

Another theory is that people are exposed to more new foods now that we're a more international community.

Then there's the belief that by avoiding foods like peanuts early in life, people may not handle them well when they experience them for the first time, whether later in childhood or as an adult. Whatever the reason, it's important to know that you absolutely can develop new food allergies as an adult.

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What's the best way to get an accurate diagnosis?
An allergist can give you a blood test to measure IgE antibodies -- substances produced by your immune system in response to an allergen -- against eggs, shrimp, peanuts, tree nuts, soy, and other suspected triggers.

Some physicians do skin-testing, just like they do for hay fever, but it's a little trickier for foods because sometimes only a fresh food, not an extract, will elicit a reaction. The blood and skin tests are considered equally reliable -- but you can't rely only on testing. Many people will test positive to a particular food, but they can still eat that food without a problem.

Can unexplained weight gain, digestive problems, or fatigue be symptoms of food allergies?
No. Food allergies are usually associated with itching, rashes, hives, or, in severe cases, swelling of the mouth and tongue, difficulty breathing, or low blood pressure. Digestive problems, fatigue, or weight gain are not symptoms of food allergies.

People with these symptoms may have lactose or gluten intolerance (an intolerance is a digestive response, not an immune response), irritable bowel syndrome, depression, stress, or some other medical problem.

Is it true that some allergists are having people consume small amounts of foods they're allergic to in order to build up tolerance?

Yes, some doctors are beginning to do oral desensitization, but it's still experimental. It's also very risky, so this is not something to try at home! Researchers are also working on developing a peanut-allergy vaccine. It's interesting research, and there is a real possibility of success, but this isn't likely to be available in the next five years.

In the meantime, the best things you can do are to know what you're allergic to and avoid it.

We hope that there will be a cure someday.