A couple of my students told me about this little "trick." Take a piece of Big Red gum and remove the wrapper. Lick the wrapper and place on your skin (shiny side out). The forehead works great, especially for the unsuspecting.
After a few minutes, the effect will be noticeable. A burning sensation is eventually accompanied by a bit of skin irritation. Try it. This is what my arm looked like after 5 minutes (the picture's not great, but you get the point):
Of course, there is chemistry at play here. The culprit is the same thing that gives Big Red (and other cinnamon-flavored gums) it's character... cinnamaldehyde.
I wonder if there is an MSDS for Big Red. If there was, I bet chewing it would not be acceptable.