BAKERSFIELD, Calif. -- Thirty million people think they have a food allergy. A small number develop rashes or serious life-threatening reactions after eating shellfish, peanuts, wheat or other foods.

But of those who believe they're allergic, most in fact, are not.

Researchers in California reviewed more than 12,000 articles on food allergies published. They found that the true incidence of food allergies hovers somewhere around 5 percent for adults and 10 percent for children.

Three kinds of tests are commonly used to determine a food allergy: a skin test, the most common, where a particle is used to prick the skin for a reaction; a blood test that looks for antibodies associated with particular foods; or a food challenge where small amounts of suspected foods are introduced to watch for an allergic reaction.

Half the time the skin test and blood tests are wrong, researchers discovered.

The report suggested that doctors should not rely solely on either test. Researchers said they hoped new guidelines will be released to better diagnose and manage food allergies.