Birch trees release their pollen in the spring, although they’re not the only cause of springtime allergies. (A variety of other plants, especially other trees, also bloom at this time). If you’re allergic to birch pollen, you are more likely to have oral allergy syndrome (OAS), which can cause your mouth to tingle or swell when you eat certain fruits. Heat can destroy the proteins that cause this reaction, so you may find that it’s uncomfortable to eat fresh apples but that you are fine with apples that have been cooked in a pie.
Aside from apples, other fruit allergies that are more common if you have a birch allergy include almonds, apricots, carrots, celery, cherries, hazelnuts, kiwis, parsley, peach, peanuts, pears, plums, and soy.