Material guide · 12
Material guide: menthol — cool is not a smell; it is your temperature receptor being tricked
· 14 min read
In 2002 two labs independently described a cold- and menthol-sensitive receptor (CMR1/TRPM8, later understood to be one channel) — so "cool" is somatosensation, not smell, and the two labs' heads went on to share the 2021 Nobel Prize. In the catalogue, laevo-menthol has 114 suppliers and dextro only 9: the market tells you which form nature makes.
First, a question most people never think to ask: why is mint "cool" when the thermometer has not moved?
What matters
- "Cool" is not a smell; it is touch. Menthol activates TRPM8, the cold receptor in your skin and mucosa, and your nerves report a temperature drop that never happened. Two labs made the discovery independently in 2002 (later understood to be the same channel), and the related research programme went on to a Nobel Prize.
- It is a solid crystal (mp 41–44 °C). Like vanillin, make a solution before formulating. High strength: the database itself says evaluate at 10% or less.
- The catalogue's isomer lesson: laevo 114 suppliers, racemic 38, dextro just 9. Natural mint makes the laevo form, and the market has voted with supplier counts.
The record
| Main item | laevo-menthol |
| CAS | 2216-51-5 |
| Formula | C₁₀H₂₀O |
| MW | 156.27 |
| Appearance | colourless crystals (mp 41–44 °C) |
| Odour | peppermint, cooling, mentholic, minty |
| Strength | high (evaluate at 10% or less) |
| Substantivity | 32 h (20% solution) |
| Registers | GRAS, JECFA, CoE, FEMA GRAS, IFRA |
Plain reading: CAS is the material's ID number; the formula matches citronellol's (C₁₀H₂₀O), another pair of "same atoms, different wiring, utterly different lives". As for that "cooling" entry among the descriptors, it is exactly what this guide takes apart: strictly speaking it is a body sensation that happens to live in the odour column.
The truth about cool: a double discovery in 2002
In 2002, two laboratories independently and almost simultaneously published discoveries later understood to be the same channel.
The Julius lab (Nature) cloned a receptor from trigeminal sensory neurons:
This cold- and menthol-sensitive receptor, CMR1, is a member of the TRP family of excitatory ion channels, and we propose that it functions as a transducer of cold stimuli in the somatosensory system.
The Patapoutian lab (Cell) reported TRPM8 in the same period; later work established it and CMR1 as one channel, and that is the name that stuck:
Here we describe the cloning and characterization of TRPM8 […] Cells overexpressing the TRPM8 channel can be activated by cold temperatures and by a cooling agent, menthol.
Put the two papers together and, plainly: your skin and the lining of your mouth and nose carry a molecular cold switch (TRPM8), and menthol is a chemical key to that switch. The temperature never changes, the switch flips anyway, and the brain receives "cool".
The two labs' heads, Julius and Patapoutian, went on to share the 2021 Nobel Prize in Physiology or Medicine for the temperature- and touch-receptor research programme. The chill in your nose runs on Nobel-grade biology.
The direct meaning for perfumery: "cool" travels the trigeminal path, the touch wiring; smell rides a separate line. So in practice it may not fade in step with olfactory fatigue's adaptation rules. In actual evaluation you may notice the chill outlasting the smell; that is an observation from smelling practice, and the papers make no such claim.
To put cool, irritant heat and warmth on one map, read Why can a scent feel cold, hot or warm?.
Smelling it (and feeling it)
- Evaluate at 10% or less; for once the database says so explicitly. Strength is rated high, and excess cooling turns into sting, the trigeminal border of pain.
- Score the smell and the cool separately, two lines in the notebook. Menthol's smell is actually clean and thin; the cool is its real body. I learned this the slow way, after strip notes that just said "minty" told me nothing a week later. Good practice for the record-keeping article's fixed vocabulary.
- It is a crystal. Weigh the solid, dissolve to a 10% stock in ethanol or DPG, then formulate (the weighing article's routine).
- Use less than you think: fractions of a percent read clearly in a formula, and its usual job is lending a breeze to something else.
The catalogue's isomer lesson
| Item | What it is |
|---|---|
| laevo-menthol (114 suppliers) | the left-handed form — what natural mint makes; the market's workhorse |
| dextro,laevo-menthol (38) | the racemate (half and half) — the synthetic route's product |
| dextro-menthol (9) | the right-handed form — niche uses |
| menthyl acetate (11) | the acetate — softer, tea-and-fruit toned, quietly cool |
| peppermint oil (88) | the whole essential oil — menthol plus a plant's worth of complexity |
114 against 9. The linalool guide taught the mirror-image lesson in words; here the market gives the same answer through supplier counts.
Regulatory
Listed on GRAS, JECFA, CoE, FEMA GRAS, IFRA. As always, registers carry no limit values. Menthol is everywhere in oral and skin products, but high-dose cooling turns to irritation. For skin formulae consult the current IFRA Standards and the supplier's specification, and start conservative.
Buying it
- Buy laevo-menthol: the natural form, 114 suppliers, the widest choice.
- Crystals keep well. Solids outlast liquids, so there is no freshness race here.
- For cool without bite, pair with menthyl acetate or blend through peppermint oil.
→ Laevo-menthol in the database: full properties, supplier list, suggested pairings. → Peppermint oil | Menthyl acetate | Search by odour: try "minty cooling" for its neighbours.
References
D. D. McKemy, W. M. Neuhausser & D. Julius, Identification of a cold receptor reveals a general role for TRP channels in thermosensation, Nature, 416(6876), 52–58 (2002). PMID 11882888
A. M. Peier et al., A TRP channel that senses cold stimuli and menthol, Cell, 108(5), 705–715 (2002). PMID 11893340