It's possible your dog could be allergic to a protein source...beef and chicken are the most common protein sources that a dog is allergic to.
I highly suggest trying Nature's Variety Instinct canned. They come in several protein sources. Each contains only one protein source and is grain-free. I suggest trying the rabbit, duck, or venison.
www.naturesvariety.com
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.