When Kasey had a seriously upset stomach and had to be re-hydrated at the vet, we were told to give her something bland like boiled chicken or hamburger. Well, I thought it would be a treat to give her boiled hamburger since she'd not had that before -- and she turned bright red, as if she had a sunburn, and became really itchy. She is allergic to beef -- and to so much else! It took me a while to find the right dog food, and to stick with it -- but now I give her ONLY her dry dog food (Artemis) and it's made a world of difference. Check out this site to evaluate some of the foods, including the one you're using:
Dog Food Analysis - Reviews of kibble I found it very helpful. Good luck!