Why does it sting to put alcohol on a cut?
I know it disinfects, but why does it sting?
Answer: It has to do with VR1 receptors. These are receptors surrounded by your skin that respond to heat. When you burn your hand on the stove, those receptors convey your brain you're burning and you pull your hand away, suddenly of course. Alcohol actually lowers the threshold of the VR1 receptors so that a lower steam sets them off. Inflamed tissue (like injured tissue around a cut) is even more vulnerable. The threshold is lowered to the point that even your own body heat can set the receptors off. So the sensation you feel is rather literally a burning sensation. .
While it is killing the germs, the chemicals that are doing that naturally sting the cut. :) When its cleaning the natrual sharp in it burns your skin while cleaning.