Menthol is an organic compound derived from mint oils. This waxy, crystalline terpene occurs naturally in mint plants including peppermint and spearmint, although it can also be produced synthetically. Because of its cooling sensation, due to an ability to chemically trigger cold receptors in the skin, menthol is widely used to relieve throat irritation and minor external pain.
What is menthol?
Though not the most prominent terpene in cannabis, menthol is probably the most familiar. Best known as an additive to cigarettes, menthol is useful for tobacco manufacturers not only for its refreshing scent and taste, but also for its ability to reduce coughing. There is conflicting research about menthol's role in cigarettes, with some scientists claiming that there is little to no correlation between smoking menthol cigarettes and developing lung cancer. Other researchers have found limited evidence that menthol cigarettes are more harmful than non-menthol cigarettes, with slightly worse cardiovascular effects noted in one study. The U.S. Food and Drug Administration (FDA) is currently seeking a ban on menthol cigarettes, but no final decision has been reached.
So, how does menthol affect cannabis users, and is there cause for concern? There is one key difference between menthol in cigarettes and in cannabis: menthol (sometimes synthetic) is added to cigarettes, while the terpene occurs naturally in cannabis. The possible issue with menthol in cigarettes is that it can cause people to smoke more than they normally would since coughing is tempered. Further, there is no proof that menthol in any form is dangerous to inhale at low levels, and it may actually present real or perceived benefits.
Some people on prescription medication may opt to inhale their medicine through menthol-rich cannabis, as the terpene can serve as an anti-irritant. Topical salves containing menthol are another option as they may reduce acute pain. Finally, menthol crystals have been tapped by natural healers to treat respiratory infections.
Menthol in everyday life
For non-smokers, the most common source of menthol in everyday life is found in cough syrups and lozenges. Menthol is also an ingredient in some pain-relieving ointments and nasal inhalers. Hard candies, breath fresheners and other sweets made with mint flavoring will give you a taste of menthol. In natural medicine, some people apply a few drops of peppermint oil to the temples for headache relief. Possessing a lower content of menthol, spearmint oil is sometimes used to alleviate an upset stomach.
Therapeutic properties of menthol
Significant research exists on menthol's therapeutic properties in the realm of pain relief as well as in reducing inflammation and oxidation.
Many studies have been performed to understand how menthol serves as a pain reliever. One study, published in the journal Rehabilitation Research and Practice in 2014 found that topical menthol application significantly reduced pain intensity among people with symptoms of carpal tunnel syndrome. An Italian study uncovered how menthol could increase the pain threshold in mice during a battery of tests, thus demonstrating how the terpene can act as an analgesic agent. Another study, published in 2018 in the Journal of Clinical Pharmacy and Therapeutics discussed menthol's role in benefiting a wide range of painful conditions.
Since pain is often due to inflammation, especially of the muscles, it is not surprising that menthol also exhibits anti-inflammatory properties. A 2016 study published in Frontiers in Pharmacology found that herbal preparations with concentrations of menthol in the 30% to55% range were effective in decreasing inflammation in animals with a parasitic disease.
One study published in PLos One in 2014 probed menthol's abilities in both antioxidant and anti-inflammatory roles. Researchers tested the effects of orally administered menthol on animals that suffered from gastric ulcers. The results revealed that menthol had antioxidant and anti-inflammatory properties in addition to gastroprotective abilities.
Role of menthol in cannabis
Dozens of cannabis varieties contain menthol. Green Monster, Wonder Woman OG, Himalayan Gold, Cabbage Patch and Space Needle are just a handful of methold weed strains on today's cannabis market. Another terpene found in cannabis, isopulegol, is designated as the precursor to menthol. So, even though strains with this terpene aren't technically menthol weed, you may still experience an icy or numbing sensation when smoking weed with either of these terpenes.
The best known of the terpenes present in cannabis, menthol is recognizable for its minty flavor and cooling sensation that acts as a minor pain reliever.
Major contributions from Dr. Adie Rae.