A curious fact about medicinal natural products is that even today their science is often murky. Menthol is one example. Plants in the mint family produce menthol in their oils, and it has been used as a non-opioid pain reliever for thousands of years. But until the last few years, nobody knew exactly how it works. Here is what science knows now.

When used topically (meaning on the skin), menthol relieves pain by several mechanisms. For one thing, it acts in a very selective way to trigger the body’s natural sensors that are known as cold receptors (TRPM8 if you want the exact name), which is why menthol creams feel cool when we rub them on. That cooling effect counteracts irritation. Menthol also stimulates and then de-sensitizes nociceptors, which are a type of pain sensor in the body. But wait, there’s more. Menthol can activate central analgesic pathways; basically, it blocks ion channels so the nerves cannot fire off pain signals. And menthol also makes blood vessels dilate to improve blood flow; in that sense, it’s a bit like caffeine. Meanwhile, scientists are trying to figure out whether they can use mechanistic insights from menthol to develop advanced new pain relievers.

Just don’t dip yourself in a vat of it. When menthol concentrations get way too high, it starts to have opposite effects.

Want to read the science for yourself?

• J.V. Pergolizzi Jr., R. Taylor Jr., J.A. LeQuang, and R.B. Raffa, The Role and Mechanism of Action of Menthol in Topical Analgesic Products, J. CLIN. PHARM. THER., 43(3):313-319 (June 2018), Epub. Mar. 10, 2018, at https://onlinelibrary.wiley.com/doi/pdf/10.1111/jcpt.12679

• R. Pan, Y. Tian, R. Gao, H. Li, X. Zhao, J.E. Barrett, and H. Hu, Central Mechanisms of Menthol-Induced Analgesia, J. PHARMACOL. EXP. THER., 343(3):661-672 (December 2012), Epub Sep. 5, 2012, at http://jpet.aspetjournals.org/content/343/3/661.long