On my lower back (read: upper buttcrack, much further up than the anus), I have a small skin tear, less than an inch long. It is red and shallow. Sometimes when I press toilet tissue to it there will be a small dot of blood, but it is a very little amount. I am at a normal weight and follow proper hygiene routines. What is causing this and how can I treat it? It generally goes away within 4-6 days, but I would like to prevent them from appearing.