Dog biting himself???

[crusto2k3]

told by who? if it wasn't a vet you shouldn't have listened. Take your dog to the vet now, or give it to someone who will take care of it.

When plugs of hair are being bitten out you MUST seek professional help.

Yeah, it could be a diet issue, which can cause skin allergies or irritations. A vet could tell you after some bloodwork.

[Night Wolf]

could be a skin rash