Bally Fitness Slimmer Belt?

I recently bought this slimmer belt w/ zipper from Bally Fitness. After i took it off when i came home from working out, i noticed my skin felt a little itchy? is it from the belt? I never felt itchy before, this is my 1st time using a slimmer belt. Also, do you wear it over your clothes or under your clothes? The picture on the box has the woman wearing it over her clothes, but my mom helped me and put it underneath and a little over my underwear. I found it uncomfortable when some of the upper part of my panties were kind of wet with sweat(sorry to gross anyone out).