Menthol is a monoterpenoid alcohol (C10H20O) that is found predominantly in Mentha (mint) plants, such as spearmint and peppermint. But it’s also prevalent to varying degrees in certain cannabis cultivars. 
Known for its minty fragrance and flavor, menthol is often added to oral and topical products thanks to the soothing properties that it possesses. This cooling sensation is why the terpene is often added to cough syrup and cough drops to open the airways and soothe the throat from irritation. Menthol acts on the TRPM8 receptor, which regulates cold sensation.
The terpene can also help relieve irritation of the respiratory system when inhaled. Tobacco companies often add menthol to their cigarette products to make inhaling more comfortable; menthol can help to minimize throat irritation and coughing . But with cannabis, menthol is naturally present, which is useful for those who prefer inhalation.
The cooling sensations of menthol can also be effective for those who utilize cannabis topicals for pain, since the terpenoid may help reduce the perception of pain thanks to its antinociceptive properties.  Research has shown that menthol increases the pain threshold of rodents when applied topically and may be considered an effective natural analgesic. Menthol also activates kappa-opioid receptors which are also involved in pain relief. 
Rubbing essential oils containing menthol on your temples can also help to relieve headaches.  It may also be effective in curbing feelings of nausea that sometimes accompany severe headaches, like migraines. 
There’s also some evidence suggesting that menthol may help calm certain side effects of cancer treatments.  Applying topical menthol may serve as an analgesic therapy for neuropathic pain caused by these treatments. 
Menthol may have antibacterial and antifungal properties and can help slow or stop certain bacteria and fungi from growing.  Menthol has also shown to be an antioxidant and anti-inflammatory agent.  Research has shown that menthol increases the activity of certain antioxidant compounds and enzymes, and may have an immunomodulatory effect that can reduce levels of pro-inflammatory cytokines in the digestive system. 
Menthol might be a common ingredient in some of the more popular consumer products, like chewing gum, over-the-counter products, and essential oils, but there is a lot more to the terpene than just its minty aroma and taste, or cigarettes.
- Delgado-Povedano MM, et al. Untargeted characterization of extracts from Cannabis sativa L. cultivars by gas and liquid chromatography coupled to mass spectrometry in high resolution mode. Talanta. 2019;120384. doi:10.1016/j.talanta.2019.120384. Times Cited: n/a, Impact Factor: 5.339
- Millqvist E, et al. Inhalation of menthol reduces capsaicin cough sensitivity and influences inspiratory flows in chronic cough. Respiratory Medicine. 2013;107(3):433–438.doi:10.1016/j.rmed.2012.11.017. Times Cited: 30, Impact Factor: 3.095.
- Galeotti N, et al. Menthol: a natural analgesic compound. Neurosci Lett. 2002;322(3):145-8. Times Cited: 277, Impact Factor: 2.180.
- Haghighi AB, et al. Cutaneous application of menthol 10% solution as an abortive treatment of migraine without aura: a randomised, double-blind, placebo-controlled, crossed-over study. Int J Clin Pract. 2010;64(4):451-6. Times Cited: 33, Impact Factor: 2.613.
- Fallon MT, et al. Cancer treatment-related neuropathic pain: proof of concept study with menthol—a TRPM8 agonist. Support Care Cancer. 2015;23(9):2769–2777. Times Cited: 46, Impact Factor: 2.698.
- Singh R, et al. Antibacterial and antioxidant activities of Mentha piperita L. Arab J Chem. 2015;8(3):322-328. doi:https://doi.org/10.1016/j.arabjc.2011.01.019. Times Cited: 153, Impact Factor: 4.762.
- Rozza AL, et al. The gastroprotective effect of menthol: Involvement of anti-apoptotic, antioxidant, and anti-inflammatory activities. Plos ONE. 2014;9(1):e86686. Times Cited: 68, Impact Factor: 2.740.