By Greg Argos

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PHILADELPHIA (CBS) — Tomato pie, rustic Italian, cheesesteaks and, of course, there are the foods we just don’t enjoy. But what about the stuff we eat which we’re allergic to?

Turns out millions of Americans think they are. According to research in the Journal of the American Medical Association, 19 percent — nearly one in five adults — believe they have a food allergy.

But it turns out 10.8 percent actually do, which means millions of Americans may be misdiagnosing themselves.

Ha Nguyen is a registered dietician at Yummy Body Nutrition. She says she has clients who think they may have a food allergy but actually may just have a food intolerance.

“If you’re allergic to a particular food, it’s life-threatening, it could be fatal. If you’re intolerant to something, you might be able to have those particular foods in small quantities,” said Nguyen.

“If someone comes in and says they get bloating, or diarrhea, constipation, more GI discomfort, that’s more intolerance than an allergic reaction,” Nguyen adds.

And she says it’s important to get a professional opinion if you aren’t sure if that peanut butter sandwich may not sit well with your stomach or could cause a more dangerous reaction.