Many dogs are allergic to different grains that are in your commerical dog food. I recently found in an odd way that my dog, Duke, is allergic to corn.
I was making some corn, as it is ripe in our area, and decided to let Duke lick the bowl when I was done. As soon as he was done eating he was rubbing his face and wiping his face on the floor and furniture. I've seen him do this a few other times when eating different things, but never put two and two together until now. I will no longer be feeding him any leftover corn or any treats, foods, chews, etc. that have corn in it.
As you know Poochieheaven recommends a grain free dog food that comes in great flavors such as Bison, Chicken, and Beef.