Skin issues in hypothyroid dog - what's the best plan of attack?
Background: My dog Heinz is 5-6 year old GSD, history unknown before I picked him up as a stray in March. When I found him, he had bilateral hair loss and smelly, shedding skin. He was diagnosed as hypothyroid and started on thyroxine and treated for a yeast infection. At the time, he was eating NutroMax lamb or chicken and rice + Innova turkey/chicken canned food. He put on weight and started growing in hair nicely.
Then came the fall. In October, I noticed the skin on his belly was blackened and starting to thicken in his "legpits". I (stupidly) let his thyroid meds run out and he was off them for about a week before I took him back into the vet. We started him up on the meds again at a higher dose for his now higher weight, and a recheck 3 weeks later gave us a "low normal" reading of serum T4. He was still itchy, though.
I changed his dry food to Fromm's grain free salmon and duck plus the Innova wet food every day. He started itching even more and losing hair. I increased his thyroid med dose again and it seemed to stop the hair loss, but the itching continued, and he was starting to smell "yeasty" again.
This weekend, he started shaking his head a lot, and I cleaned his ears twice in 3 days. Two days ago he was holding his left ear flat to his head and listing like the Titanic. So off to the vet we went. She diagnosed an ear infection, and we took blood to see where his thyroid level is at. The vet also noticed all the irritated skin and said "Wow, his skin is in awful shape and he looks really uncomfortable" - which he was, I guess I didn't realize just how bad (and I feel even worse now). So now he's on a short course of prednisone, a couple of weeks' worth of ketoconazole, a month of antibiotics, and two types of ear drops to combat the ear infection.
SO, my question is now this - assuming the steroids and the antibiotics get this under control and the free T4 comes back normal, what is the best thing I can do to prevent this from happening again? Vet recommended switching his food to Royal Canin Skin Support, as she has seen some dogs do very well on that. I'm willing to give that a try, and I figure if I don't see improvement in a month or so, then I'll do allergy testing and go from there.
Does this seem like a reasonable plan of action? I'll admit to being a little wary about the food - I know Royal Canin doesn't have the best track record in terms of safety and food recalls and the food lists rice as the first ingredient, followed by "fish meal". However, I do trust the vet when she tells me she's seen it work for other dogs.
Any advice or suggestions would be welcome!