Dogs and cats are just as prone to allergies as you or I. Food allergies and sensitivities, ticks and mites and even their own food supply can cause unnecessary suffering for your pet.
Not all pet food is created equal. Unfortunately, there are some pet foods with more "filler" than nutrients. Large and medium breed dogs are especially susceptible to food allergies from the "fillers" used in inferior dog foods. If your dog suffers intense itching or daily diarrhea, he may be allergic to his own food supply. Many dogs don't tolerate cornmeal well, the main ingredient in many cheaper foods. Try switching your dog to a meal that is more hearty or natural, and watch for signs of improvement.