Although food and diet fads come and go, there is general agreement that we should eat more raw fruits and vegetables. Uncooked fruits and vegetables are the richest source of vitamins, minerals and antioxidants- nutrients often lacking in our over-processed, carbohydrate and fat-loaded, American diets.
For many people with pollen allergy, however, eating fruits and uncooked vegetables is not an option. When they do, the result is often intolerable itching and irritation of the mouth, palate, and throat, and If they eat too much or too fast, they can develop abdominal pain and symptoms of a full blown allergic reaction.
This condition is called the oral allergy syndrome or pollen-food allergy syndrome and occurs when the antibodies that cause seasonal allergy symptoms, usually directed at grass, tree, or weed pollen, react with similar proteins found in food. For example, patients with ragweed allergy may have problems with bananas, cucumber, and melons because these contain proteins that are similar to proteins found in ragweed pollen. When these anti-ragweed antibodies in the mouth and throat come into contact with the food, a mild allergic reaction occurs with itching and mild swelling. So eating a banana or piece of cantaloupe ends up making you feel like you just ate a bowl of fresh ragweed leaves.
In the same way, if you are allergic to birch tree pollen you may have problems eating a variety of fruits, vegetables, and nuts including apple, peach, apricot, cherry, plum, pear, almond, hazelnut, carrot, celery, parsley, caraway, fennel, coriander, aniseed, soybean and peanut. Birch trees are common throughout the northern United States and Europe but are rare in Arizona. However, allergy to Arizona Sycamore, a tree common to mountain and transition zones of Arizona, has been associated with reactions to apple, hazelnut, lettuce, corn, kiwi, peach, and peanuts, and green beans. Sensitivity to Mugwort, an allergenic weed also prevalent in the Northern United States and Northern Europe, can cause reactions to carrot, celery, parsley, caraway, fennel, coriander, aniseed, bell pepper, black pepper, garlic, and onion as well as mustard, cauliflower, cabbage, and broccoli.
More important to the Southwest is sagebrush sensitivity, which is associated with reactions to carrot and celery.
An important distinction between the oral allergy syndrome and other types of food allergy is the rare occurrence of more serious allergic symptoms. This is because the proteins in the fruits and vegetables that cause the oral allergy syndrome are very fragile and easily destroyed by digestive enzymes in the mouth and stomach. So by the time the food leaves the mouth or stomach, the body no longer recognizes it as an allergen. Cooking also denatures or destroys the allergenic proteins so that foods that cannot be tolerated when raw can be eaten after cooking. This works out for banana bread and apple pie but cooked watermelon is just not the same.