Some dogs have allergies to whole grains. Our Cookie lost nearly all her fur from scratching and biting until we switched to a No Grain dry food. The one that has worked amazingly well for us was the Nutro Natural Choice No Grain formula. We chose the Venison and Potato flavor.
The difference in her coat and in her scratching level is astounding. Even our vet couldn't believe the difference. He said, "She's gorgeous!"
She still has some hot spots under the arms but overall, much improved almost immediately after switching from corn meal based food.