What type of food do you feed? You may need to buy a better quality food such as, canidae.
He might have fleas. I am not positivly sure. If I were you though, I would go see a vet.
Are you bathing him? Bathing is a very special occasion thing, as they do have sensitive skin that dries out when soap is used. Also the first couple years I had my Beagle Clyde ( 100% pure 7 years old) he itched and developed into gnawing (as if scratching with his teeth not eating) and licking of his toes. They smelled slightly yeasty. It was determined he cannot eat dog food with grain, since moving him to rice and lamb or other non-grain dry foods the itching constant licking and chewing on his feet have completely stopped. Hope that helps..... but having a vet look at your pup when they display worrisome symptoms is always a good idea.