My 2 1/2 yr old Maltese seemingly overnight developed a large bald spot on her back above the thigh --- it's not red, itchy or inflamed, and the skin is smooth. Tests for ringworm, mites were negative and I was told it could be either food or environmental allergies, leaving me in total limbo as to which it could be. My vet told me to give her melatonin to restore the hair but it's been over a month and I don't see any new hair growth. Has anyone else had a similar problem??? I've googled every dermatology web site and nothing listed seems to fit her situation...most atrophy begins at the head area or appears on both sides of the body or is more common in different breeds.