I feed Royal Canin to 3 of my yorkies before. Their hair grows long and beautiful, but I also found they have flaky skin since I start to use Royal Canin. One of my yorkies has really bad flaky skin, so I stop feeding him Royal Canin. I use Avoderm instead. After feeding him Avoderm, less than 5 days, I found it truly improved that. About 1 week or so, his flaky skin is gone. I also found his hair becomes softer. I was amazed how effective Avoderm dog food is.
If anyone's yorkie has flaky/dry skin, try Avoderm. You can see the result very soon.