Menthol

Aroma and sensory profile

Menthol is the definition of cool. Fragrance references type (−)-menthol mentholic with high odor strength and describe it at 10 percent as peppermint, cooling, mentholic, and minty, with a flavor typed cooling and described as cooling, camphoreous, minty, clean, and spicy [1]; the Merck Index, as compiled by PubChem, calls it simply a peppermint odor [4]. The cooling is not a smell but a sensation, felt on the tongue, the skin, and the airways.

The molecule is a cyclic monoterpene alcohol with three stereocenters, giving eight stereoisomers, and the enantiomers differ sharply. (−)-menthol, the natural form, is the one described above. (+)-menthol is described only as characteristic, and fragrance references note that it is not found in nature [2]; it cools weakly and carries a musty, less clean note. The racemate is described at 10 percent as peppermint, cool, and woody, with a cooling, mentholic, minty flavor [3]. The 2013 review of menthol chemistry states that natural menthol is isolated exclusively from cornmint and that the (−) form, natural or synthetic, is the preferred isomer [5].

Effects and research

Menthol has more human evidence than any other compound on this site, because it is a drug. Its mechanism was settled in 2002 with the cloning of TRPM8, a channel expressed in cold- and pain-sensing neurons that is activated by cold temperatures and by menthol [6]; the cooling sensation is that channel firing.

The clinical trials are recent and specific. A 2025 meta-analysis of 14 randomized trials in 1,002 patients found that (−)-menthol delivered into the breathing circuit during gastrointestinal endoscopy reduced peristalsis (odds ratio 3.88) and improved procedural ease (odds ratio 2.53) with adverse events comparable to placebo [7]. In 60 breast cancer patients on paclitaxel, topical 1 percent menthol applied twice daily to hands and feet significantly improved chemotherapy-induced peripheral neuropathy over six weeks compared with standard care [8]. In 20 patients with COPD, inhaled menthol during cycle exercise reduced the intensity, unpleasantness, and air-hunger quality of breathlessness without changing exercise endurance [9]. The 2013 review catalogues antibacterial, antifungal, antipruritic, anticancer, and analgesic activity and menthol's use as a skin penetration enhancer [5].

The other human literature is tobacco. Menthol in cigarettes cools the smoke and eases inhalation, and its restriction has been the subject of bans in Europe, Canada, and US states; a 2025 scoping review of 25 studies found variable behavioral responses to those bans, from quitting to product switching, across regions [10].

Natural sources

Menthol is a mint terpene, and one mint above all. HSDB records that (−)-menthol is the main component of peppermint and cornmint oils from Mentha piperita and Mentha arvensis, and that most (−)-menthol is obtained from cornmint oil, with a pale yellow oil of Lantana leaves reported to carry 8.2 percent [4]. The 2013 review states that natural menthol is isolated exclusively from cornmint, Mentha canadensis, and that the rest of the world's supply is made synthetically to the same structure [5]. Fragrance references note its occurrence across mint species [1] and that the (+) form does not occur in nature at all [2]. Cornmint oil is frozen and centrifuged to crystallize menthol out, leaving the dementholized oil used in flavoring. Spearmint carries almost none; its cooling comes from carvone. In cannabis menthol is not a native terpenoid; reports of it usually reflect added flavoring.

Boiling point and vaporization

PubChem compiles menthol's boiling point as 212 °C from the Joint FAO/WHO Expert Committee on Food Additives, the Merck Index, and the PhysProp database, and 421 °F from the National Toxicology Program, with a melting point of 41 to 43 °C [4]; fragrance references list 212 to 216 °C at 760 mmHg [1][3]. This profile keeps 212 °C (414 °F), the JECFA value, which matches what the site already listed. That places menthol with linalool and isopulegol in the heart-note band. As a solid melting near 42 °C, pure menthol softens in a warm hand and sublimes slowly at room temperature. As a saturated alcohol with no double bond it is oxidation-stable. No thermal degradation study of menthol was found.

Safety and regulation

Menthol is listed by the US Food and Drug Administration as a permitted synthetic flavoring substance at 21 CFR 172.515, as "Menthol; 2-isopropyl-5-methylcyclohexanol" [12], and is a regulated active ingredient in over-the-counter topical analgesic, antipruritic, and cough products. The Research Institute for Fragrance Materials assessed it in 2022 [11]. No cancer classification applies.

Its skin record is that of an irritant, not an allergen. Under Europe's classification inventory, 98 percent of notifications flag (−)-menthol as a skin irritant and 32 percent as a serious eye irritant, with no sensitization code above threshold [4]. The clinical trials reported adverse events comparable to placebo by inhalation and topical use [7][8][9]. The caution is that of a potent sensory drug: the tobacco literature is a reminder that a pleasant cooling agent can make a harmful product easier to use [10].

Industries and uses

Fragrance: menthol supplies the cooling note in mint, fougère, and fresh accords and is stocked as (−), (+), and racemic grades [1][2][3]. Culinary: it holds FDA flavoring status and is the defining component of peppermint flavor in confectionery, oral care, and beverages [1][12]. Aromatherapy: peppermint and cornmint oils are its carriers; the inhalation trials in endoscopy and COPD are the best human evidence for a cooling vapor on this site [7][9]. Pharmaceuticals: menthol is an over-the-counter active with randomized trial support for itch, neuropathy, and dyspnea and a defined receptor [6][8][9]. Cosmetics: it is used across cooling and oral-care products, with the irritation classification that formulators track [4].