What is this itch between my legs?

I have been experiencing a constant itch in my anal region for a number of months now, and instead of getting better, it's getting worse. It started as just an itch on my anus, but has since propagated in a straight line between my legs both forwards and back. It is now impossible to go a day without scratching, and in doing so, it seems i'm removing dead skin, sometimes in flakes. it seems that in scratching I am making it worse, but it is unbearable not to within 2 minutes of it acting up. I just looked in a mirror, and noted a single red line stretching from front to back across the intersection of my legs. Thoughts on what this might be? No, I have not had any sexual relations in my life.