This!!!! I used to be a big Iam, Science Diet consumer. I had nothing but problems with my felines on these diets. Renal failure, urinary problems, etc. I learned I was feeding my cats fillers and chemicals. Science Diet, especially the Vet diets, were preserved with BHT, BHA and other nasties. It was very concerning to learn what I had been feeding them, especially at the price I was having to pay!
I'm currently dealing with a very allergic cat. After a year, I still have been unable to solve his problems even with the Vet approved science diets. So, I read most cats are allergic to chicken, fish, beef, dairy etc. So why do the vet diets that are specifically made for allergies contain chicken? And starches? And eggs? And soy? The cheapest ingredients on the market produce the highest priced pet foods on the market. Think about that.
I don't know what I'm going to do about my feline friend. Shots didn't work, different protein sources didn't work, limited ingredients didn't work. Vet diets didn't work. I am down to just digging old meat out of my freezer and removing all carb sources and I still see him biting and scratching daily. Three quarters of his hair is gone (just what he can't reach is left) and he has sore bumps all over his body. I've tried just about everything available on the market with no improvement and am now, like I said, trying to just feed a slightly cooked meat diet, which I really can't afford anyway.

Too bad he can't tolerated chicken or eggs. Figures.