A very common reason for biting the feet are fleas.
Is your dog biting other parts of his body? Look carefully at your dog’s belly. Do you see any tiny black specks?
If you do, these are flea feces. Give him a good flea bath and treat his feet carefully. Wash his bedding and anything else he sleeps in or plays with.
It would be nice if we could just treat the dog with the newest and best flea treatments.
But this is not the case. You have to wash the bedding in very hot water and spray the area with flea killer that your dog spends most of his time.
My areas are the bed area, all the windows and the couch and my bed!