I have been using Royal Canin Hydrolyzed Protein Hypoallergenic food for Pebbles who was always itching. It's been a life saver to her. I now have all 3 on it and they are doing very well. It is an RX food that I purchase from the vet but I had tried all the Limited Ingredient foods out there.
You could try switching to Natural Balance Limited Ingredient. They have many different varieties and they are all guaranteed so if they don't work out you can return them for a different formula. Petco and Petsmart take returns on opened bags of food.
I really like the Royal Canin Yorkshie Terrier formula but RC doesn't come in a LI food.
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