I know what you are talking about! Mitzi was almost bold on her back and her paws. I first changed to home cooked food and it got much better but I was always worried if she would get all the vitamins and minerals. Purina and Iams are not the best dog foods out there and they contain corn and wheat which can trigger allergies. Just a few days ago I bought
Eagle Pack Lamb and Rice Holistic dog food and it looks like she is doing good with it.
My Vet also recommended "Physoderm" shampoo (the one for acne) and that helps also.
I hope your furbaby is going to get better very soon!