I tried to post earlier and kept getting "page cannot be displayed."
Anyways, a lot of dogs itch because thier food has a lot of corn and poor quality ingredients in it. Dogs express food allergies through their skin by itching. I've learned all of this because I have a dog that is allergic to corn in his food, and corn pollen (and we live in the Midwest, poor dog!).
Read your food bag. If you see the word "corn" change food. "Expensive" foods don't cost any more than cheap grocery foods becaues you don't have to feed as much of it, because it's more nutritous (My 100lb dog only eats 4 cups of food a day, he'd need at least twice that, on food that costs half what I'm feeding now....do the math! LOL!). My rule of thumb is if the brand isn't advertised on TV, it's got a chance at being good food. I have yet to see a brand of food advertised on TV that I would feed my pets.
Just go to a pet store (grocery stores don't carry any good food) and start reading bags.