I have 3 dark/scaly patches (circles) on my back, and one big one at the top of my buttcrack. My posture when sitting is very bad, either severely hunched over or my butt at the end of the chair with the top-buttcrack/lower back on the chair. The 3 small marks on my back are where the spine bumps or whatever rub against the chair because of the way I sit. As for the buttcrack, I seem to sweat a lot down in that area, and am not sure if it is normal or not. I was prescribed something that I have been applying, but it doesn t seem to help, for what they said was irritated eczema. I ve never noticed any eczema symptoms anywhere else, and think they might have given me the wrong stuff. I m just wondering what else this could be, and how to fix it.