Hello,

While I am not a vet, I have learned a lot about cats and cat
nutrition. Have you considered that he might have a food allergy?
Things like corn are common allergens in cats. IMO I would try feeding
him a high-quality wet diet, one with NO grains, for 6-8 weeks, and
see how he does. IMO I would not feed him any Hills/prescription food.
If you look at the ingredient list, it is scary. There are much better
diets out there, like Nature's Variety (canned or raw), Innova Evo
(canned), Wellness (canned), among others.

Good nutrition will help him in many ways. Any dry food doesn't have
enough moisture in it, and too many carbohydrates. Here is a great
nutrition web site with lots of information: http://www.catinfo.org

Rene