Oral Allergy Syndrome (OAS) is an allergic reaction caused by allergens found in certain raw fruits and vegetables, as well as some nuts. It is usually more mild than systemic nut allergies, which can be fatal. OAS is most common in older children, adolescents, and young adults who have been eating the foods in question for years without any problem. Toddlers younger than 3 years old typically do not develop allergic rhinitis (hay fever) until they are older.
People with OAS are often allergic to pollen from birch, ragweed, or grass. The proteins found in these foods are similar to pollen proteins, so the body reacts the same way it would to an allergen from a tree, herb, or plant. The foods that trigger OAS symptoms depend on the other allergies a person has. Nuts such as hazelnuts and almonds can cause reactions in people with OAS. My 8-year-old son Tommy has food allergies and OAS to many things that cross-react with his pollen allergy. If you have hay fever and your mouth or throat itches after eating certain raw fruits or vegetables and some nuts, you may have symptoms of Food Pollen Allergy Syndrome (PFAS), also known as Oral Allergy Syndrome.
To avoid triggering an allergic reaction, it is important to know which foods to avoid if you have OAS.