I used to have a combination of dermatophagia and dermatillomania. I don't get it as much now because I developed trichotillomania, I think my skin picking and biting moved over towards hair pulling, now I seem to have more of a problem with that.
I am a wolf bitter and met a fellow wolf bitter here. I don't do it so much anymore thankfully. Definitely an anxiety disorder along with all the other things listed on this thread. I still can't leave my nails alone very well. I have never had a manicure which would be amazing I think...and helpful.