Pollen Food Allergy Syndrome (PFAS), also known as oral allergy syndrome, is caused by cross-reacting allergens found in both pollen and raw fruits, vegetables, or some tree nuts. The immune system recognizes the pollen and similar proteins in the food and directs an allergic response to it. People affected by PFAS can usually eat the same fruits or vegetables in cooked form because the proteins are distorted during the heating process, and the immune system no longer recognizes the food.

PFAS typically does not appear in young children. The arrival is more common in older children, teens and young adults who have been eating the fruits or vegetables in question for years without any problems. Young children under the age of 3 do not usually develop allergic rhinitis (hay fever) until after they are toddlers. Hay fever is associated with reactions to the pollens that cross-react with the foods Those with PFAS typically have allergy to birch, ragweed, or grass pollens.

If you feel like you’re always getting an itchy mouth after eating the same raw fruit or vegetable, it’s time to speak to an allergist.