Allergic reactions to fruit are commonly associated with oral allergy syndrome (OAS). It’s also known as pollen-food allergy. OAS occurs from cross-reactivity. The immune system recognizes the similarity between pollen (a common allergen) and the proteins in raw fruits, vegetables, and tree nuts. That recognition triggers an allergic reaction in some people. Here are the types of pollen and their related fruits that may trigger an OAS reaction: Birch pollen: apple, apricot, cherry, kiwi, peach, pear, and plum. Grass pollen: melon, orange Ragweed pollen: banana, melon Mugwort pollen: peach