My maltese had some unexplained hair loss on his face, I took him to the vet on several occasions and could not get a reason for it. I gave him a homeopathic product that worked wonders it was $20 and that was nothing compared to what I spent at the vet. He had bare spots on his face with no hair at all and in 1 week of giving him 3 drops daily I was able to see very visible results. Here is the link, they also sell it on amazon for cheaper.
Newton Homeopathics Pets Skin Care-newtonlabs.net