Listen to Cathy - I learned the hard way. Though the skin itches and hurts, it was worth wiping/washing everything off 6 hours before the appointment. If I didn't, my skin hurt like I never want to feel again. If necessary, I'd take a sleeping pill to get me through those six hours.
I felt like I was going through tubs of Aquaphor, but it was worth it in the end.
Sabrina