"Some people have allergic symptoms in their mouth when they eat certain fruits and vegetables that are fresh but not when they're cooked. And that's very interesting -- we call that oral allergy syndrome," Liu said.
The reason, Liu explained, is that cooking destroys the problematic allergens in these foods.
"In the fresh state, they cause allergic symptoms usually limited to the mouth, but sometimes it can also affect breathing," he said. "But when those fruits or vegetables are cooked, then the allergens are broken down, and they no longer cause symptoms."
This is also the case with food oils. A person with a soy, corn or safflower allergy is unlikely to be allergic to soy, corn or safflower oils because the processing and purification breaks down the allergens. However, because peanut oil is typically less processed, it is still a potential allergen for a person with peanut allergies.
ABC News' Radha Chitale contributed to this report.