What is the best hypoallergenic dog food?

According to PetMD, the best hypoallergenic dog food depends on the pet's allergies. No single food is hypoallergenic for dogs with all types of allergies. Rather, hypoallergenic foods should be chosen based on a dog's allergy.

Dogs can be allergic to most of the main ingredients in dog foods, such as pork, beef, chicken, lamb, fish, rabbit, soy, wheat, egg or dairy, according to WebMD. The dog's food allergy must be identified before selecting a hypoallergenic food, since the food needs to exclude the right allergen. Common hypoallergenic foods exclude wheat and soy, but this does not help a dog that is allergic to chicken or egg, for example.