I feed and sell Canidae and have seen it clear up some pretty nasty allergies like you described. Ones where the owners were giving the pooch eight benedry/day at their vet's advice and the poor canine was still losing hair and biting itself.
But, sometimes even a holistic food won't help if there is one ingredient in it your pet is supersensitive to. And I'll assume that along with the natural foods you fed (which Iams is not), that you also stopped with the garbage treats that contain wheat and corn and soy and sugar.....
One of my customers can only feed NB Duck and Potato and that is also the treats she must buy. Another of my customers is having her dog allergy tested because nothing she is trying is working, along with the predisone pills.
Also, allergies can be related to environment, too. Those pet powders you put down before running the sweeper..... they are for us, not your pet. They are often the cause of a dog's allergies, or any of a multitude of floor cleaning products where your pet spends most, if not all of their time.
And a poor coat can also be a sign of a thyroid problem. For some reason, a thyroid imbalance seems to be the vets last thing they test for..... and I've seen it be the root of the problem probaby 80% of the time.
And I would go back to feeding raw before I bought EVO. That stuff is expensive! Even at cost. And what if your dog is allergic to chicken? And the other one contains beef, which a lot of dogs are allergic, too.
At any rate, please keep us (or me) posted. I would love to hear how everything turns out and what ended up working.
Good luck!