In some children, food allergies often produce flares of atopic dermatitis . Another common manifestation of food allergy is the "oral allergy syndrome," in which certain foods cause itching or hives where they touch the lips and mouth. Fresh fruits and vegetables are often associated with this kind of reaction. These reactions are believed to be due to pollen protein cross-reactions (responses to fruits and vegetables frequently occuring as clusters of hypersensitivity to members of the same botanical family, for which the immunologic basis lies in a number of common allergens) in the fruits, which are inactivated by cooking. For example, persons sensitive to ragweed pollen may develop hives on the lips while eating melon. Similarly, people sensitive to birch tree pollen may react to fresh apples. The same people, however, might tolerate cooked apples, as in apple pie.