Just thought I would add a little in here for those who might be interrested. Look at the ingredients of your animal food next time you are thinking about it. The main ingredient on most foods sold cheap (ie. at WalMart) is corn or corn meal.
Corn isn't in the cat and dog's normal diet. This corn is what many think leads to animal allergies, gas and other digestive and skin ailments.
Look for the more expensive food that has lamb or other actual meats as the main ingredient. You can expect to pay near double depending on the food, and might have to go to a real pet store to get it.
My lab has been fed the good stuff his whole life and he doesn't have any skin issues or allergies and i often get comments on his shiny coat. (I don't bathe him more often either. usually about once a month.)
I don't claim to really know what I'm talking about as far as pet nutrition, just someone talked to me about this and it really made sense.