What is the best allegry medicine for shrimp allegry? I would like to try shrimp again.

None. There are no medications that are effective as a pre-treatment for food allergy. That is, there is nothing that you can take before a meal to prevent a reaction to ingesting a food to which you are allergic. There are several treatments under development, but none have been shown to be highly effective. The only treatment for food allergies at this point is to avoid the food.