My 7 year old bulldog has developed some sort of skin rash we can not get a diagnosis for. It started out with a few small patches of thinning fur and baldness on his back legs but has now quickly spread up his back. With much larger bald patches which are red and flakey, some with scabs and what appears to be dry skin? We have had many tests at the vets and ruled out mites flees and ringworm. We had blood tests which came back as some allergies to grass and trees however he is not exposed too much too these nor has his surroundings changed to bring this progress rash on. We are at a loss as we simply don't no how to treat it. Wondering if anyone has had similar problems or has any tips to ease itching and dryness. Thanks so much