I have always felt relief from removing dead/flaky skin and picking at acne. I pick and bite at my lips a lot and in the winter I pick at my dry scalp. I have left some scars from picking pimples. I always thought that the urge to do this sort of stuff was human nature but my OCD tendencies have at times driven me to be over zealous and pick when I shouldn't (hence the scarring). I try to be conscious of what my hands are doing (apparently when you're tired you're more likely to "pick" at things without realizing) and to stop it before I go too far. I remind myself of how what I'm doing might leave a scar or make me bleed. Anyway I don't think this is something to feel ashamed about, I think its normal human behaviour but it is magnified by our OCD (with different ranges of it depending on how severe the OCD is).