Material guide · 69
Material guide: alpha-hexyl cinnamaldehyde — the jasmine molecule jasmine doesn't make, third most declared allergen, near the bottom in the clinic
· 27 min read
CAS 101-86-0. It appears in 157 of 954 formulas (16.5%) at a median dose of 8.00%, among the heaviest-dosed materials this series has covered. Its odour field says jasmin; its occurrence field says chamomile. GHS flags H317 for skin sensitisation, and a 2018 survey of 1,447 products across 131 households found it among the three most frequently declared allergens — while a 2007 study of 21,325 patch-tested patients put its sensitisation rate at 0.1%, near the bottom of the EU's 26. It differs from alpha-amyl cinnamaldehyde by one carbon, and that carbon moves the household IFRA limit by an order of magnitude.
Start with two fields side by side.
Odour field: fresh; floral; green; jasmin; herbal; waxy; sweet; citrus; fruity; powdery; tropical; spicy
Occurrence field: chamomile
It smells of jasmine, and where nature does make it, it is chamomile. Jasmine does not make this molecule.
Today's other piece counts how many kinds of jasmine a supplier stocks, one class being reconstitutions — fifteen or twenty materials approximating the whole impression of the real flower. This is the main beam in those.
The short version
- It appears in 157 of 954 formulas (16.5%) at a median dose of 8.00%, putting it among the heaviest-dosed materials in this series.
- The odour field says jasmin and the occurrence field says chamomile. A 2015 study of four commercial jasmines found linalool, farnesene and benzyl acetate on top — not this.
- Substantivity 400 hours at 100%, strength medium. Shelf life is only 12 months, short for this series.
- GHS flags H317 (may cause an allergic skin reaction). Two datasets point opposite ways on that:
- On labels: a 2018 survey found the 26 EU declarable allergens named almost 2,000 times across 1,447 products in 131 households, and the three named most often were limonene, linalool and hexyl cinnamal.
- In the clinic: a 2007 study of 21,325 patch-tested patients put its sensitisation rate at 0.1%, near the bottom of the 26.
- It differs from alpha-amyl cinnamaldehyde by one carbon. That carbon puts an order of magnitude between their household IFRA limits (Category 9: 19% against 1.5%).
About 8 minutes.
How common, and how heavily dosed
In the 954-formula deduplicated corpus:
| Value | |
|---|---|
| Appearances | 157 / 954 (16.5%) |
| Median dose | 8.00% |
| Suppliers | 56 |
One formula in six uses it, at a median of 8%.
We built the ladder from strength label to dose: materials labelled medium sit at a median of 2.00%. This one is labelled medium and goes in at four times that.
The gap describes its job. It is not there to give an impression; it is there to carry volume — the sort of material that fills out a floral, standing alongside phenethyl alcohol at a median of 10.00%.
Its substantivity is 400 hours at 100%. That figure is high for this series: Calone reads >600 hours but at 10% dilution, and veramoss's 400 hours is also at 10%. This 400 was measured neat.
Jasmine does not contain it
This is the thing worth remembering about this material.
Bera and colleagues used GC-MS in 2015 to measure the headspace scent of four commercially cultivated jasmines (sambac, auriculatum, grandiflorum, multiflorum). The constituents topping all four:
- major monoterpene: linalool
- major sesquiterpene: (3E,6E)-α-farnesene
- most abundant benzenoid: benzyl acetate
No cinnamaldehyde derivative on that list.
And the database gives its occurrence as chamomile. It is an industrial synthetic — a condensation product of hexanal and benzaldehyde — rather than something pulled out of a flower.
So why is it called a jasmine aldehyde? Because it lands on several facets of jasmine: green, waxy, fruity, powdery. Inside a reconstitution it pushes the whole toward the direction of jasmine rather than reproducing any molecule that is in jasmine.
That has a direct consequence for buying. If you want the complexity of the real flower, this cannot give it to you — Braun and colleagues characterised 121 compounds in one jasmine absolute. If you want a stable, affordable jasmine direction that does not shift with the harvest, this exists precisely for that.
One carbon from alpha-amyl cinnamaldehyde
There is a pair of twins on the market that people confuse:
| alpha-hexyl cinnamaldehyde | alpha-amyl cinnamaldehyde | |
|---|---|---|
| CAS | 101-86-0 | 122-40-7 |
| Formula | C₁₅H₂₀O | C₁₄H₁₈O |
| Corpus appearances | 157 (16.5%) | 70 (7.3%) |
| Median dose | 8.00% | 6.00% |
| Substantivity | 400 hours at 100% | 256 hours at 100% |
| Suppliers | 56 | 53 |
| Occurrence | chamomile | soybean, black tea |
One carbon on the side chain, 144 hours of substantivity, and more than double the market uptake.
What really separates them sits in another column.
| GHS | hexyl | amyl |
|---|---|---|
| Sensitisation | H317 | H317 |
| Aquatic | H402 / H412, harmful | H401 / H411, toxic |
One says harmful, the other says toxic. And that difference is visible in IFRA Amendment 49:
| IFRA category | hexyl cinnamal | amyl cinnamal |
|---|---|---|
| Category 4 (fine fragrance) | 9.9% | 7.0% |
| Category 9 (household cleaning) | 19% | 1.5% |
| Category 10A (other household) | 69% | 1.5% |
Comparable in fine fragrance, an order of magnitude apart in the household columns.
And that line runs all the way to the back of your detergent bottle. Wieck and colleagues surveyed detergents in 131 households in Regulatory Toxicology and Pharmacology in 2018, searching the ingredient lists of 1,447 products for the 26 fragrance allergens the European Detergents Regulations require to be named.
Those 26 appeared almost 2,000 times, and the ones named most often were limonene, linalool and hexyl cinnamal.
On household labels it is the hexyl, not the amyl. The table above offers a coherent reason.
(To be clear: that study counted labels and drew no causal conclusion. Putting the IFRA limits next to the labelling frequencies is my own reading, not a finding in either paper.)
What H317 means, and what it doesn't
The GHS entry for this material carries H317: may cause an allergic skin reaction. People usually take a step back at that line.
The clinical numbers point elsewhere.
Schnuch and colleagues reported IVDK data in Contact Dermatitis in 2007: across four six-month periods from 2003 to 2004, 21,325 patients were patch tested with the 26 EU-labelled fragrances in addition to the standard series, with between 1,658 and 4,238 patients tested per substance.
Standardised for sex and age, the top and bottom of the list read:
| Fragrance | Sensitisation rate |
|---|---|
| tree moss | 2.4% |
| HMPCC (Lyral) | 2.3% |
| oak moss | 2.0% |
| hydroxycitronellal | 1.3% |
| isoeugenol | 1.1% |
| … | |
| amyl-cinnamic aldehyde | 0.1% |
| hexyl-cinnamic aldehyde | 0.1% |
| limonene | 0.1% |
| benzyl benzoate | 0.0% |
0.1%, near the bottom of the 26.
The paper also draws a useful distinction: substances with higher sensitisation frequencies were characterised by a considerable number of "++/+++" reactions, while those with low frequencies showed a high number of doubtful or irritant reactions and few strong ones.
Their conclusion is blunt: among these 26 there are fragrances which are, with regard to contact allergy, of great importance, others of minor importance, and some of no importance at all.
Stack the two datasets and you get this: it is among the three most frequently declared allergens on labels, and among the least frequently confirmed in the clinic.
A label lists what must be declared, not what is risky. That list of 26 was produced by rule rather than sorted by measured sensitisation rate. We've written about reading safety studies, and this is a clean example.
None of which means H317 can be ignored. Already-sensitised people do react, and 0.1% of 21,325 is still more than twenty people. The point is that this line should worry you less than the oak moss line, and in practice it is the oak moss line that deserves the worry.
IFRA's 9.9% against the corpus's 8.00%: a units trap
Put the two numbers side by side and it looks alarming:
- IFRA Category 4 (fine fragrance) limit 9.9%
- Corpus median dose 8.00%
It reads as though half the formulas run right up against the regulatory ceiling.
The units are different.
- IFRA's percentage is concentration in the finished product.
- The corpus percentage is a share of the concentrate.
Finished perfume usually dilutes the concentrate to 10-20%. So 8.00% of a concentrate becomes 0.8% to 1.6% in the finished product, nowhere near 9.9%.
This trap is worth flagging on its own, because both numbers are written with a % sign. We covered the same point in the IFRA piece, and this material is where it most easily bites, because the two figures happen to sit close together.
Physical properties
| Property | Value |
|---|---|
| CAS | 101-86-0 |
| Formula | C₁₅H₂₀O, MW 216.32 |
| Appearance | pale yellow to yellow clear liquid (est) |
| Boiling point | 174-176 °C at 15 mmHg |
| Flash point | 113 °C |
| logP | 4.80 (est) |
| Water solubility | 2.75 mg/L at 25 °C (est) |
| Shelf life | 12 months or longer |
| Suppliers | 56 |
| Regulatory listings | JECFA, FEMA GRAS, CoE, FLAVIS |
The 12-month shelf life is worth noting. Most materials in this series start at 24 months — phenethyl alcohol and veramoss both do. Aldehydes oxidise more readily, and if you plan to dose at 8%, a stale bottle rewrites your formula.
Water solubility of 2.75 mg/L sits four orders of magnitude below phenethyl alcohol's 22,000 mg/L. This one does not go into a water phase.
What this doesn't establish
I have not smelled it and have made no comparisons. The whole piece sets database fields, the formula corpus and papers against each other.
"Jasmine does not make this molecule" rests on the occurrence field and Bera's headspace analysis. Headspace measures what a living flower emits, not an absolute. A trace present in an absolute but invisible to headspace cannot be ruled out from what I have. The industrial source being synthesis, however, is not in doubt.
"The household limit gap comes from aquatic toxicity" is my inference. The two tables were looked up separately, IFRA does not explain in the text how a limit was derived, and aquatic toxicity is a coherent explanation rather than a demonstrated cause.
Wieck's study counted mentions on ingredient lists, not actual content. A product naming it says nothing about how much is in it. That study measured no product.
Schnuch's population is dermatology-clinic patch test patients, not the general public. A clinic population is enriched for people with skin problems, so 0.1% would be lower in the general population rather than transferable to it.
That data is from 2003-2004. Market usage shifted over twenty years and so did exposure. Lyral (HMPCC) sat at 2.3% then and was subsequently prohibited by IFRA, so that ranking no longer holds.
The substantivity comparison (400 against 256 hours) comes from two database records, both marked 100%, which does not guarantee one experiment or one method.
The GHS classification is what the database records, not a complete regulatory determination. Work from the SDS for your own batch and the current IFRA standard.
References
A. Schnuch, W. Uter, J. Geier, H. Lessmann, P. J. Frosch, Sensitization to 26 fragrances to be labelled according to current European regulation. Results of the IVDK and review of the literature, Contact Dermatitis, 57(1), 1-10 (2007). PMID 17577350. doi:10.1111/j.1600-0536.2007.01088.x
S. Wieck, O. Olsson, K. Kümmerer, U. Klaschka, Fragrance allergens in household detergents, Regulatory Toxicology and Pharmacology, 97, 163-169 (2018). PMID 29940212. doi:10.1016/j.yrtph.2018.06.015
Related: a supplier listed five jasmines, what IFRA limits actually limit, how to read fragrance safety studies, the starter palette map.