My veterinarian worked with UC Davis veterinary nutritionists (who created the above site) to formulate a custom recipe for one of my dogs who is highly allergic to a world of things, including most meat proteins.
In addition to their on-line questionnaire that creates a recipe based on your dog's needs, the site also sells their own supplements and blends to mix with the food to assure proper nutritional requirements and make it easy for pet owners. They also include in their recipes a list of the individual supplements you need, in case you don't want to buy their brand.
You might give it a try. My dog, who had been unable to tolerate every top-shelf and/or hypoallergenic brand of commercial and prescription dog food we tried has been doing quite well now for nearly 3 years. I make his food using the recipe formulated by some of the folks who created the above website. I wouldn't hesitate to use and recommend this service now, whether dealing with a completely well dog or one with medical issues.