Have you tried the various "premium" foods?
Like Acana
or
Orijen
or
Taste of the Wild
Purina do a hydrolysed diet.
Royal Canin too.
Found this too:-
Other Options to Consider
Hydrolyzed protein diets are one option owners of dogs with food allergies can try, but they may not work in all cases. If your dog’s symptoms do not improve with a hydrolyzed protein diet, you may want a commercially prepared hypoallergenic diet that features unique sources of protein and carbohydrates that may not create an allergic reaction in your dog.
If a hypoallergenic diet doesn’t work, you may want to try a bones and raw food (BARF) diet, which uses a combination of foods similar to those wild dogs eat, such as:
fat
muscle meat
organ meat
bones
This omnivorous diet is believed by many to be healthier for your dog, but it may require an unusual meat source to be successful for your dog, which may be allergic to beef or poultry since both are commonly used in commercial pet foods.
Copyright © 2010 VetInfo.