Oral allergy syndrome (also known more accurately as pollen-food allergy syndrome) is an allergy to certain fruits, vegetables, and nuts that causes itching, tingling, redness, or mild swelling of the mouth, lips and throat when the food is eaten in uncooked form. Although more common in adults, OAS occurs in children, too. The symptoms result from pollen-related proteins found in these foods.
Children who have OAS may experience a “funny feeling” or mild anxiety when they begin to have symptoms. For most patients, when the food is swallowed and digestion begins, gastric acid and digestive enzymes disrupt the protein and the symptoms promptly fade.
What causes OAS?
Children usually have allergies to pollen first and then develop OAS later. In fewer cases, OAS is the main complaint, and allergy symptoms such as nasal congestion and eye itching are not as bothersome. There may be an increase in the number of foods causing symptoms over time. However, many children with pollen allergies will not go on to develop OAS symptoms at all.
Apples and bananas are two of the most common OAS culprits. Apples are in the same family as birch tree pollen, so when a child experiences OAS with apples, the reaction may actually be related to tree pollen allergy. Similarly, bananas and ragweed are closely related. Because the fruit and pollen cross-react, OAS symptoms may occur more often during and right after pollen season. In that case, the offending food should be avoided during and immediately following the corresponding peak pollen period. For example, those with OAS to apples should avoid eating them during tree pollen season in the springtime and also in early summer. In general:
- Birch pollen allergy may be associated with reactions to apple, peach, pear, plum, cherry, carrot, celery, almond, hazelnut, and legumes.
- Grass pollen allergy may be associated with reactions to melon, orange, white potato, tomato, and peanut.
- Ragweed pollen allergy may be associated with reactions to banana, melon, cucumber, and zucchini.
Sometimes in OAS, symptoms occur with only one food, while other times, there are reactions to multiple foods. Peeling the fruit and eating only the pulp can lead to a decrease in symptoms for some children. In most cases of OAS, symptoms only develop when children eat the raw, uncooked form of the food. Most children can tolerate the offending food when it is cooked or baked. Tree nuts and peanuts causing OAS are an important exception though, since even roasted nuts can still cause symptoms. It’s also important to note that non-plant foods such as cow’s milk and egg do not cause OAS.
Is OAS ever life-threatening?
For most patients, symptoms of OAS are mild and resolve quickly without intervention. However, there are some children who may develop more severe symptoms such as hives over the body, vomiting, or trouble breathing. If a child has any of these symptoms after ingesting any type of food, seek medical attention right away. If your child has symptoms that suggest OAS, it is important to see an allergist to confirm that there is indeed pollen allergy, and to discuss testing and treatment. It is especially important to see an allergist if your child has any of the following, since these can be signs of a more serious allergy:
- Symptoms involving more than the mouth or throat, for example hives, vomiting, sneezing, or wheezing
- Symptoms that are moderate to severe rather than mild
- Symptoms due to peanuts, tree nuts, or mustard
- Symptoms with cooked forms of the food
Is there effective treatment for OAS?
Avoidance of the offending plant foods in their raw form, especially during and just after the cross-reacting pollen season, is the best way to prevent symptoms. Strict year-round avoidance may not be necessary for all patients. Also, children may eat the foods when they are cooked and do not cause symptoms. In general, children with OAS should avoid eating large amounts of the offending raw food at once, especially on an empty stomach, and stop eating the food all together if symptoms seem to be getting worse over time. OAS is usually a lifelong condition, unless the patient is treated with immunotherapy (allergy shots) for the underlying pollen allergy. Allergy shots are very helpful for pollen allergy, and for a number children, OAS symptoms improve with this treatment as well.