Material guide · 18
Material guide: cinnamaldehyde — cinnamon's heat sits on the same family of switches as menthol's cold
· 16 min read
CAS 104-55-2, the body of the cinnamon smell. The menthol guide covered TRPM8, the cold switch; cinnamaldehyde presses another one in the same family, TRPA1, and the 2004 study found it the most selective at activating that channel among the compounds it tested. It is also one of the fragrance allergens the EU requires on labels, and a 1996 threshold study measured the concentrations and delayed reactions in already-sensitised subjects. 105 suppliers, 212-hour substantivity; this is where heat in perfume comes from.
The coumarin guide mentioned cassia cinnamon, with coumarin hiding inside it. But the hot rush that fills your mouth and nose when you bite a cinnamon roll belongs to a different molecule: cinnamaldehyde.
What matters
- Cinnamaldehyde is the body of the cinnamon smell, and most of the heat in perfumery comes from it. High strength, evaluate at 10% or less; 212 hours of substantivity make it base-note material.
- Menthol presses the cold switch, TRPM8. Cinnamaldehyde presses another in the same family, TRPA1. Read the two guides together and you have both ends of temperature perception.
- It is one of the fragrance allergens the EU requires on labels. For people already sensitised to it, a 1996 study measured the concentration range that triggers reactions. Check the IFRA limit before it goes on skin.
The record
| CAS | 104-55-2 |
| Formula | C₉H₈O |
| MW | 132.16 |
| Odour | sweet, spicy, aldehydic, aromatic, balsamic, cinnamyl, resinous, honey, powdery, cassia |
| Odour family | spicy |
| Strength | high (evaluate at 10% or less) |
| Substantivity | 212 h (neat, on a strip) |
| Specific gravity | 1.046–1.050 (25 °C) |
| Flash point | 93 °C |
| Shelf life | 24 months or longer (cool, dark, sealed) |
| Registers | GRAS, JECFA, CoE, FEMA GRAS, IFRA |
Plain reading: CAS is the material's ID number. Specific gravity above 1 means this one sinks in water. 212 hours puts it in the series' long tail, standing with clove and the balsams. Beginners tend to miss "honey" and "powdery" in the descriptors; diluted, that sweetness actually arrives before the burn.
The heat switch
A recap first. The menthol guide explained that mint's cool is a molecule pressing the cold receptor TRPM8, no thermometer involved. Cinnamaldehyde is the same story from the other side. Bandell and colleagues, Neuron, 2004:
Six members of the TRP ion channel family respond to specific temperature thresholds. […] pungent compounds from cinnamon, wintergreen, clove, mustard and ginger oils activate TRPA1. […] Cinnamaldehyde, identified as the most selective activator among them, stimulates cold-sensitive sensory neurons and produces nociceptive responses in mice.
The authors read these results as mechanistic insight into why noxious cold can paradoxically feel like burning pain. The "hot" on your tongue is a channel built for reporting irritation being pressed by a molecule. Neurons and mice are mechanism, and say nothing about what happens to a person wearing perfume; but set beside menthol's TRPM8, both ends of temperature perception now have a molecule that presses them. For formulation the practical part is this: when a composition needs warmth, it usually comes from the same plants. Cinnamon, clove and ginger, the oils on the paper's list, are also the regulars of the warm-spice palette.
For how TRPA1 divides the work with menthol's TRPM8 and eugenol's TRPV3, see Why can a scent feel cold, hot or warm?.
What sensitisation looks like in numbers
Cinnamaldehyde is one of the fragrance allergens the EU requires on ingredient labels, and IFRA sets a limit standard for it. To see what sensitisation actually looks like in people, Johansen's 1996 dose study in Contact Dermatitis is a classic:
In cinnamic-aldehyde-sensitive subjects we ran serial dilution patch tests and 6-week graded use tests with 0.02, 0.1 and 0.8% cinnamic aldehyde in ethanol. […] 6 of the 13 use-test-positive subjects (46%) reacted later than day 7. […] A significant correlation between patch test sensitivity and the outcome of use testing was found.
Two things to hold onto. First, every subject was already sensitised to cinnamaldehyde; the concentration figures describe that group, not the general population. Second, nearly half the reactions arrived after a week. "I wore it three days and nothing happened" does not clear a material — of everything in this literature, that is the reminder I use most.
Smelling it
- High strength; the database says evaluate at 10% or less. The first neat sniff made me cough, and the honey layer only turned up around 1%.
- The heat has a dose threshold: a trace reads warm, too much reads burning. A few tenths of a percent lifts the temperature of an amber or oriental accord.
- It forms a natural trio with vanillin and coumarin. The cinnamon-roll kit.
- For anything going on skin, look up the current IFRA Standard for cinnamaldehyde in your product category before setting the dose. This is one of the materials with an actual limit value.
The catalogue family
| Item | What it is |
|---|---|
| cinnamaldehyde (105 suppliers) | the material itself: cinnamon's heat |
| alpha-hexyl cinnamaldehyde (56 suppliers) | the hexyl version; the burn mostly gone, drifted to a jasmine-side floral aldehyde, a soap regular |
| alpha-amyl cinnamaldehyde (53 suppliers) | the amyl version; floral again, the backbone of old jasmine formulas |
| alpha-methyl cinnamaldehyde (34 suppliers) | the methyl version, a gentler cinnamon |
| ortho-methoxycinnamaldehyde (32 suppliers) | the methoxy version, a supporting player in cassia |
Lengthen the side chain and the burn gives way to flowers. Hexyl and amyl smell like a different world from the parent, yet the names differ by one prefix. Read carefully before ordering.
Regulatory
Listed on GRAS, JECFA, CoE, FEMA GRAS, IFRA. Unlike most materials in this series, IFRA sets a limit standard for cinnamaldehyde, and EU cosmetics regulation requires it named on the ingredient list above a threshold. For skin formulae, consult the current IFRA Standards for your product category and the supplier's specification.
Buying it
- A small bottle lasts. High strength plus a limited-material identity keeps formula doses low anyway.
- Check for CAS 104-55-2 so you do not land on the hexyl or amyl florals.
- Start with a 1% dilution. The dose window for "warm" is narrower than you expect; smell the ladder once yourself.
→ Cinnamaldehyde in the database: full properties, supplier list, suggested pairings. → Alpha-hexyl cinnamaldehyde | Search by odour: try "spicy sweet" for its neighbours.
References
M. Bandell, G. M. Story, S. W. Hwang, V. Viswanath, S. R. Eid, M. J. Petrus, T. J. Earley & A. Patapoutian, Noxious cold ion channel TRPA1 is activated by pungent compounds and bradykinin, Neuron, 41(6), 849–857 (2004). PMID 15046718
J. D. Johansen, K. E. Andersen, S. C. Rastogi & T. Menné, Threshold responses in cinnamic-aldehyde-sensitive subjects: results and methodological aspects, Contact Dermatitis, 34(3), 165–171 (1996). PMID 8833458