I Have A Reoccurring Bumpy, Somewhat Itchy Rash Area In

I have a reoccurring bumpy, somewhat itchy rash area in one area of my body. This rashy spot is on my buttocks. I don't know what it is or how I got this . I do not scratch it and I apply rubbing alcohol to the area and the rash leaves, but leaves a reddish spot where it will sometime occur again.