I'm having the same problem with my puppy. He will be 18 weeks this Friday and I've notice a lot of hair is falling out. I brush him at least twice a day and spray him before doing so. His lower back has about 3 or 4 very small areas where you can see the hair has fallen out. Otherwise his coat is soft and shinny so I'm also quite curious as to why this is happening.
__________________  Jacky & Pepper |