A couple of weeks ago I noticed that my dog had a small bare spot on his elbow that looked like he was scratching too much. Over the past couple of weeks, the spot has gotten bigger and he's even bled a little. I'm assuming it's from biting/scratching but I've never actually seen him bitting or scratching that spot, which is kind of weird. I have an appointment for the vet in about a week or two; does anyone have any ideas of what could be causing this??