I second the raw food switch.
It is especially important for dogs with lots of food allergies to be on a raw diet, that way you are 100% sure what is going into their system and you don't have to worry about them getting sick from an allergen.
Most dogs are allergic to things like grains, soy, glutens, or other plant based products. This is because dogs are carnivores and NEED meat, bones and organs to THRIVE. Of course dogs can survive on kibbles and such...but its 100% species inappropriate.
Read thru the link that Jon posted up. Great way to get started. You will be amazed at the difference in your dog's health and well being. But make sure that if you decide to make the switch, to do it the right way. It will minimize most issues that you will come across.