The oral allergy syndrome (OAS) is a common adverse allergic reaction to the ingestion of certain raw fruits, vegetables, and nuts in people with pollen allergies. Allergens in these allergic foods are similar to the allergens in the pollens.
Some reports suggest that 25% to 50% of people with pollen allergy have the OAS and up to 75% of people with birch tree allergy have the OAS.
The most common symptoms of the OAS are itching and tingling of the mouth and throat usually within minutes of eating the raw allergic food. There can be varying degrees of swelling inside the mouth that is rarely life-threatening. There is less than a 1% chance of anaphylaxis which is a life-threatening allergic reaction. Your allergist will be able to inform you if you are at risk for associated anaphylaxis or not. Typically the reaction does not occur if the food is cooked or canned. For example, eating raw carrots will trigger the reaction but eating cooked carrots will not. The symptoms generally last minutes and will resolve on their own as long as you immediately stop eating the allergic food.
Listed below is an updated list from the American Academy of Allergy, Asthma, and Immunology regarding the different foods associated with pollen types that could trigger oral allergy syndrome.
| Pollen type | Season | Foods Associated with Oral Allergy Syndrome |
| Birch tree | Spring | Apple, Apricot, Cherry, Peach, Pear, Plum, Kiwi Carrot, Celery, Parsley Peanut, Soybean Almond Hazelnut |
| Timothy and orchard grass | Spring-Summer | Peach, Watermelon, Orange White potato, tomato |
| Ragweed | Late Summer-Fall | Cantaloupe, Honeydew, Watermelon, Banana Cucumber, white potato, Zucchini |
| Mugwort (mold) | Fall | Bell pepper, Broccoli, Cabbage, Cauliflower, Chard, Garlic, Onion, Parsley Aniseed, Caraway, Coriander, Fennel, Black Pepper |
