Anyone able to recommend a good dog food that won't make the Big Dog scratch?

Yes, it's me Parker, the LA English Springer Spaniel and I'm scratchin' again...is there any dog food on the market that truly won't cause me to scratch?  Been checked by the Vet for mites, fleas and others and it seems it's always food related.  Now we're back to home cooked meals of beef, pork and lamb with veggies like sweet potatoes, broccoli, cauliflower & sliced apples with a bit of vitamin E.  Any suggestions on "food in a bag" that might work? - Woof Woof, said the little dog!