Oral allergy syndrome (OAS), also known as pollen-food syndrome, is a condition where individuals experience allergic reactions to certain raw fruits, vegetables, or nuts. The symptoms typically include itching, tingling, or swelling of the lips, mouth, throat, and sometimes the ears. In more severe cases, individuals may experience systemic reactions such as hives, difficulty breathing, or anaphylaxis.
The primary cause of OAS is cross-reactivity between proteins found in certain fruits, vegetables, and nuts, and proteins found in pollen. Many people with OAS also suffer from seasonal allergies, particularly to pollen from trees, grasses, or weeds. When they eat certain raw fruits, vegetables, or nuts that contain proteins similar to those found in the pollen they are allergic to, their immune system may mistake these food proteins for pollen proteins and launch an allergic response.
For example, if someone is allergic to birch pollen, they may experience OAS symptoms when they eat raw apples, cherries, peaches, or carrots, as the proteins in these foods resemble the proteins found in birch pollen.
It’s important to note that cooking, processing, or heating these foods can often break down the proteins responsible for the allergic reaction, so many individuals with OAS can tolerate these foods in cooked form. Additionally, some individuals with OAS may be able to tolerate certain fruits, vegetables, or nuts without experiencing symptoms, as the levels of cross-reactive proteins vary among different varieties and cultivars.
Managing OAS typically involves avoiding raw fruits, vegetables, or nuts that trigger symptoms, and in some cases, allergists may recommend allergy testing or immunotherapy to help desensitize the immune system to specific allergens.