My Charlie will go through spells where he will scratch so much he looses huge clumps of fur. The most recent one left him completely bald on his butt and above his tail (yeah, he chewed off ALL of his Aussie "butt fuzz". We called him baboon butt for the longest time, hehe).

What helps him is first off making sure he has no fleas. I give him two benedryl a day -- one with each meal (one morning, one night). In addition I have a bottle of bitter apple spray on hand to spray over areas that are still really itchy. He will chew and scratch till he bleeds and has huge scabs so I try to nip the problem in the bud as soon as I see him scratching so he doesn't get to that point.

In addition, bathing too often will dry out his skin and make it even more itchier, so bathe maybe once a month (unless your vet recommends otherwise).

Bottom line though take him to a vet... if he can't help you, take him to another vet until you start getting answers. I can't stand watching Charlie scratch that bad, you can tell how miserable he is.

His are seasonal though so that's how I know benedryl works, and boy does it work well for him most of the time. Now that the weather is ice cold again and he got his bath for the month he hasn't scratched or chewed at ALL. Once it starts warming up though he'll go crazy again as he always does... certainly doesn't help that Missouri can't decide what season it wants to be in, keeps bouncing between winter and spring it seems.