Mint has been used as a breath freshener for centuries. In the middle ages, young men who were on their way to their beloved’s would alter their course in order to pass by the herb garden first. They would pull off a few peppermint leaves, toss them into their mouths, and chew them for a while in hopes of covering up the stench coming from the abscessed molar that they had yet to have the blacksmith pull.

This historical association of “mint” with “fresh breath” seems to be so ingrained in our collective psyche that nearly every toothpaste and mouthwash you buy today is mint-flavored. Listerine is, of course, the obvious exception, but its competitors mocked it so mercilessly by saying that their own products left your breath “minty, not mediciny,” that Pfizer finally relented and came out with Listermint. This just reinforced the belief that the ultimate aspiration of all human beings should be to have a mouth of which it could be said that it is “minty fresh.”

But our mouths are not enough anymore; now they want our whole heads. Nearly every hair care company has come out with some product that has mint as a featured ingredient. In fact, Aveda’s most popular product line is their Rosemary Mint Shampoo and Conditioner, whose “tonic properties of rosemary and peppermint cool and revitalize your scalp.”

But the “tonic” and “cooling” properties they are touting are not necessarily coming from the peppermint, per se, but a derivative thereof:

mint (‘mint) n. Any of various plants of the genus Mentha, characteristically having aromatic foliage and nearly regular flowers. Some plants are cultivated for their aromatic oil and used for flavoring.

menthol (‘men-“thol) n. A white crystalline organic compound, CH3C6H9(C3H7)OH, obtained from peppermint oil or synthesized, and used in cigarettes and as a mild topical anesthetic.

So, of course it leaves your scalp feeling “cool”; you’ve lost all sensation from the ears up.

I first noticed this “mild topical anesthetic” effect when using American Crew’s Daily Shampoo and Conditioner. They say that the menthol in these products “cools and refreshes the scalp,” but I found that as I rinsed the conditioner out of my hair some of it would run down my body and, if I wasn’t careful to rinse it off completely, I’d get a rather unwelcome cooling and refreshing effect in an area of my body that doesn’t usually react well to being cooled and refreshed.

This mentholic sensation is referred to as a “tingle” by the makers of Denorex, the anti-dandruff shampoo:

The tingle tells you it’s working, and Denorex leaves your scalp feeling fresh and clean!

…and numb. Come on, guys, admit it. The only thing that tingle is telling you is that you just smeared the active ingredient in Vicks VapoRub all over your head.

I firmly believe that when it comes to the bathroom:

Aromatherapy: Good
Anesthesia: Bad

And I can think of a few other rooms in the house where that axiom holds true.