I agree with switching her food. I was feeding Bailey Royal Canin for yorkies (her breeder had fed her that) and she started scratching and getting sick a lot. There is corn in that food.
I started looking for another food and found one that is grain free, Natures Variety, she loves it and her coat is very soft and she doesn't itch at all now.
Here is the link for NV to find a retail store, the store will give you free samples if you ask :
http://naturesvariety.com/content.la...E0AFuJoQ85359B
If you sign up on their site they will send you buy one get one free coupons.