For a few months now Gizmo has had a "skin condition" type deal on his shoulder. I've tried Listorine, Iodine, and medicated shampoos but with no change. It hasn't gotten any better or worse, just remains the same. It looks as if something dripped down him, as it starts at the top of his neck under his mane and then trails down to the front of his left leg. It does not seem itchy at all, I've scratched at it and he doesn't react.
When it first appeared the skin was flaky and I got all of it off so now it's just flat and hairless.
Any ideas as to what it may be or what I could do to get the hair to grow back?
Here are the pictures to give a better idea: