he could have a bacterial or fungal skin condition. usually you see hair loss, but sometimes you don't. i had a big fluffy cat who had ringworm but never lost any hair. it was one of those freak things and she had so much hair you just couldn't see the fungus without the wood's light.
otherwise, i'm with everyone else about the dry skin treatments. be careful with the oatmeal because it can absorb oil from the skin making it drier. in girl scouts we were told that if you are ever campijng and have no water to wash your hair you can always rub oatmeal on your hair to absorb the scalp oils. it should have the same effect on animals.