You might want to look at our product, Derma-IonX to help heal the skin. Derma-IonX which is an oral homeopathic product stimulates the enzyme systems in the body which reduces itching and inflammation, promotes healing of the skin and helps with assimilation of nutritional components in diet and supplements. The supplements I use along with it include digestive enzymes, probiotics, and fish oil. Together with Derma-IonX it produces a synergistic effect for a faster response. It can also be used topically if there are troublesome spots on the skin.
I would also suggest that you give your cat only filtered water for drinking and bathing if your water contains chlorine or fluoride. For the dietary modifications you might want to try a grain free diet for a while. In addition I would also have a stool sample checked for tapeworms. I have seen cats that groom themselves excessively when they have parasites.
Please feel free to contact us again if you have any other questions.