It's curious how everybody that's commented here has interpreted the OP as asking for ways to deal with scratching areas that you can't reach. I thought he meant "what do you do when you're standing in front of the whole world giving the most important speech of your life and your pubic lice begins to run rampant?"
go to a wall or tree or something like that? :P
take bar as help?
just resist it and dont care about it