Hi, I have this 1/4" to 1/2" recurring spot blister thing that keeps popping up on my shoulders and arms. They have a open wound area surronded with a blister looking spot and also there is 1 sometimes 2 tattoo looking "c" shaped marks next to it. It last about 3 to 4 weeks and leaves a dark scar! Parasite? Acme? I've been to a dermatologist and intern and there stumped! I would like to post a picture but I don't think I can on this forum. Any help would be appreciated! Thank you.