OP I had suggested dyshidrosis before.
http://en.wikipedia.org/wiki/Dyshidrosis. I get it on my thumbs and other fingers at joints. It comes and goes - is much worse when under stress and itches like hell. My internist said to use Cortizone-10 and not itch it, but when it's really going, it's very difficult not to want to tear your skin off.