I have been a skin picker - of bug bites, scrape injuries, acne, ear wax and nose matter since I was about 4 years old. I also will usually ingest what I pick. I've been involved in this behavior now for over 50 years.
I have a possible correlation that might explain my own picking behavior. It is that I highly suspect (and have for about 40 years now) that I am an alien abductee. I know both subjects are bizarre. But, I believe the incessant picking at myself is a copying of what was done to me, by non-human beings repeatedly over the years, since I was a toddler. Experiments on my body - scoop marks, triangle shapes, scrapings, eye/ear/nose.vaginal/anal areas probed with instruments too. And, maybe a tracking implant left behind in my body somewhere, that I try to instinctively pick at to claw out.
I am now 55 years old and the skin picking continues, but I believe abductions have lessened greatly from my earlier years as a child/teen/fertile adult. I sometimes have been able to keep the pickings in check by limiting the area - say the sides of my upper thighs. But, I will sometimes go into a full-blown picking fest, which I have been in now since autumn of 2008 - over many parts of my body, save for my face -- it seems as my acne abated as I grew older, my face is much less a target.
I bit my nails off to make it more difficult to pick, yet I still do it even though it is not as rewarding. I am now considering getting 'gel' nails, as I read in another post somewhere on this board, that this can be a possible deterent, I'm assuming that the natural nail does not get to 'feel' the pleasure of picking.
I do not have any memories of sexual abuse or physical abuse as a child and am quite sure I was not. When I was married my husband did physically abuse me for a short period of time, but the marriage ended within a year's time after the abusive episodes. I do however remember partial memories, throughout my lifetime, of tall Insectoid alien beings (like giant preying mantis) and short Grey alien beings - both kinds being extremely close to my eyes....staring. And then poking and prodding various parts of my body, while I'm in an induced state of temporary paralysis. Also large orb lights, acorn-shaped metalic craft and the classic saucer shaped craft. It became agony for me to have to sleep in bed at night, so by necessity, I became a nightowl for many years now and sleep in the daylight hours. I even sought out jobs that were 2nd or 3rd shifts to fit this schedule. I am now early retired though as I have enough money to live comfortably but carefully. I wanted to share this possible correlation, but am not suggesting it is a reason for other people that are pickers, only that it may make sense for me personally. Also, I am very appreciative of this Forum and the openminded owner and forum contributers.