You could give him some Vitamin E capsules or Fish oil capsules. They will help his skin. You could also put a tablespoon of Olive oil in his food. They get moisture back in their skin and they stop chewing and scratching much at all.
My dog is constantly licking and biting his back, butt, paws and tail until they bleed. How can I help relieve his pain?
I agree with Rooster, you could also try removing grains from his food and giving him a cup of plain or vanilla yogurt a day. He may have an allergy to corn which causes an overgrowth of yeast, which in turn causes itching!
Our dog has the same thing due to allergies we found that hydrocortisone spray from the pet department in your local Walmart helps with the itching