Echoing Melanie's questions on how many he's losing & whether he's actually showing thin or bald spots. You didn't mention, but is he scratching at all? Sometimes they can have mites without being able to see them actually crawling on him. If you haven't already, it may not be a bad idea to treat for them anyway, with Revolution. You'll have to go to the vet to get it, so while you're there, it may be a good idea to also have them do a skin scraping to test for fungal or bacterial infections.
~*~*~ Kelsey ~*~*~
RIP my sweet Lily ~ 6/12/08 - 1/20/12