My parents have a yellow lab and she has black itchy skin mostly on her legs. It looks almost like dirt rubbed into her skin but doesn't wash off. It's itchy to the point where she bites it raw. The vets are baffled, she tested negative for mange but then they said they'd treat her for it anyway. No help. Now they think maybe allergies. Medicated baths and wipes don't seem to help either. Any one have other remedies to try? Willing to try anything at this point!