Icy Hot

In high school, a friend once took up a bet that he wouldn't slather icy hot over a most delicately indelicate region. He took the bet for money, a move made on the assumption that it wouldn't be that bad. Mere moments after slathering the viscous jelly on himself and he was clearly regretting his decision. His skin absorbed the active ingredients, menthol and methyl salicylate, and it was sending signals his brain interpreted as the damage of rapid freezing. His brain, convinced that he was somehow accidentally dipping his testicles in a vat of frozen water, was screaming at him that something was direly wrong.

The pain and temperature nervous system runs on different wiring than the rest. Temperature transmits more slowly to your brain, allowing a period of accommodation when changing one's climate. The nerves themselves lack the complicated mechanical apparatus of the somatic sensory, ending in uncomplicated open ports that merely change elements of biological function if the temperature becomes excessively high or low. The odd thing is that these sensors can also be triggered chemically.

The menthol and methyl salicylate of the icy hot had been absorbed by his skin, percolating into his system and encountering nerves dedicated to a purpose of discussing the weather. They bind to these nerves, triggering their activity, and sending a veritable tidal wave of information to the brain, all coded to mean the same thing: Cold. It is this mechanism that makes you feel the air cool when you take a cough drop (menthol), or burns the inside of your mouth when you eat a habanero pepper (capsaicin). For some reason we have an evolutionarily designed mechanism to interpret a chemical as hot or cold, to become sweaty when eating a burrito doused in hot sauce, or to feel a cool breeze merely by contacting menthol.

Perhaps it was a far sighted evolutionary attempt to teach my friend to exert better judgement.