I had the odor with max and yes it thyroid was a bit low and he was going to a allergist, who retired! Max got bad again so now we have him on a hypoallergenic food, and he is doing so much better. Yes i tried the grain free, cooking food, this poor dog never knew whatwas going to be in his plate. If i were you i would try hypoallergenic food first, if that doesn't work then take him to an allergist/dermatologist. Feel free to pm me. Max had that odor when we rescued him. The only reason the problem came back is because I wanted to,stop the cortisone and get him on a more natural diet. I also switched vets because they were not getting him better and since then, he is, because my vet will work with me. Good luck and don't give up, i know how frustrating it can be for both.
Does he shake his ears too, besides biting his feet?