When I put Icy Hot on my hand, I can only feel the effect on the top part of my hand. Why?

Hey, Matt:

I put Icy Hot on my hand the other day because my thumb was hurting. Unfortunately I was nearly struck mute with astonishment when I found that I could feel the "icy yet hot" sensation on the top of my hand but not on the palm side at the base of my thumb. Why is this? I thought that the palms and fingertips were MORE sensitive.

-- Jeremy Barwick, Spring Valley

Well, I guess you thought wrong, bubba. But hey, the situation's epidemic. "Common knowledge" is one of those viruses you don't hear much about but is known to be the cause of most human suffering. True, true, our fingertips are loaded with nerve endings that enable us to make fine discriminations and manipulations. But your palm is designed for heavy-duty tasks -- whapping vending machines to get your change back, stuff like that. If fingertips are among the most sensitive body parts, palms are among the least sensitive (along with our backs). Fewer sensory nerve endings in your palm and at the base of your thumb. Icy Hot and other hot/cold balms work by stimulating our head and cold receptors, creating a counterirritant that takes our minds off the pain of the injury. So I guess putting the stuff on the base of your thumb wasn't such a hot/cool idea.