I'll contribute mine. Been putting it on abs for awhile. I had put it one in the early morning and the burning was gone by noon. Later that night the wife and I were going at it and I was hittin it from behind. I was working up a good sweat and then I noticed the burn started coming back. So after a good 15 minutes from behind, we finish and as she's in the bathroom peeing I hear her go "Why does my ass feel like its on fire."