Too Cool

So, it turns out that I'm rather allergic to certain moisturizers, or some ingredient therein.

In addition to some serious topical steroid cream which required a prescription, my dermatologist suggested a lotion called Sarna* as an additional treatment/source of salvation. (A salve of salvation?) What's the magic ingredient? There are two, actually: camphor and menthol.

Camphor

Naturally-derived camphor is a tree resin that is solid at room temperature. It is also highly flammable, which I learned from The Time Machine. Not surprisingly, it has some insect-repellent qualities (of course it does, plants need defenses too!). Some mothballs are made with camphor. It is also a rather effective topical analgesic.

It is interesting to note that natural camphor is derived from the camphor laurel, Cinnamomum camphora. That genus name isn't a coincidence; true cinnamon (C. verum) and cassia (C. aromaticum, which is most common "cinammon" sold in America) are in the same genus as camphor. Camphor laurels are an economically important crop in the areas where the species is native, but the tree is invasive in Australia. Camphor was also one of the first organic chemicals to be synthesized in a laboratory.

Menthol

Menthol is the other half of this dynamic duo. Menthol can also be synthesized in the lab, but in nature it is found in members of Mentha, the genus that includes peppermint (Mentha x piperita, actually a well-established hybrid of watermint and spearmint), spearmint (Mentha spicata), and other pleasant-smelling herbs.

I don't know which of these compounds acts faster and which one lasts longer, but combined they're enough to stop itching cold. (Sorry.) Menthol stimulates specific cold-sensitive ion channels in skin neurons, but I'm not sure how camphor works. In my case, the combination of menthol and camphor creates such a strong illusion of cold that I start shivering even though I know my body is at an acceptable room temperature.

I would write more -- allergies are incredibly interesting and very complicated -- but I'm also taking diphenhydramine and I feel like I'm about to zonk out. (And it's only 11 AM!) I'd better prepare some coffee.

Caffeine

Oh, organic chemistry, is there anything you can't do?

*As an interesting aside, sarna apparently means "scabies" in Spanish.