It could be a number of things allergies being one of them. I would have a vet take a look because they may want to do a skin scrape. Now saying that My Jewels when she was a pup lost a bunch of hair on her back and the vet did a skin scrape and nothing showed up. They put her on an antibiotic and her hair grew back and she had no more problems. When My other dog chachi lost hair he ended up having mitess so you never know |