Originally Posted by JanM
We tried chicken, bison, goat, beef - and possibly more (can't remember now but I do know I tried everything they had at the time). ....
How much time has elapsed between each type of food you've fed?? Please note that when dog consumes something they're 'allergic' to, those allergens can remain in their system for 3-6 months thereafter. So, if you're switching between foods within a short amount of time, it would appear that they're allergic to everything because they're still reacting to what was fed previously, or before that, or before that, etc.