I have oral allergy syndrome, so what are some healthy alternatives for snacks?

Cook the food. Oral allergy syndrome can be caused by a large variety of foods, so the answer to your question depends on the foods that bother you. Most foods that cause oral allergy syndrome are due to proteins that are destroyed by heat, so cooking the food may solve the problem.
Depends. It really depends on the raw fruits and vegetables you are having to avoid. There are probably some fruits and vegetables that you can tolerate. You should also be able to eat the fruits and vegetables that bother you as long as they are cooked.