Have you tried feeding him Innova? If not....maybe it's worth a try. Give it time though.
Believe it or not many dogs are more allergic to beef, eggs and lamb. You may have to play around with different foods to find the culprit.
Choose a product on this page to view the ingredients:
http://www.naturapet.com/display.php?d=inn-home
Then check here to find a supplier in your area:
http://www.naturapet.com/display.php?d=stores-tab