Compounds · Phenols · Phenylpropanoid pathway
Eugenol
Also known as 4-Allyl-2-methoxyphenol · Caryophyllic acid — an analysis may use any of these names
Clove, warm, slightly numbing on the tongue. Present in cassia leaf, holy basil and clove — three unrelated plants.
- CAS
- 97-53-0
- Formula
- C10H12O2
- Molar mass
- 164.20
- Odour threshold
- 8 ppbin water
- Boiling point
- ≈ 254 °C at atmospheric pressure
For this compound the two axes sit close together. Volatility tells you whether it leaves a surface early or late; the threshold tells you how much of it the nose needs before it notices.
Must be declared on the label
This compound is on the list of allergens that must be declared individually on cosmetic labels in the European Union, as one of the 24 substances listed before Regulation 2023/1545. Name to use on the label: EUGENOL.
The declaration threshold is 0.001% in leave-on products and 0.01% in rinse-off products. This is an EU requirement — see the regulations page for why it matters beyond the EU. This is not legal advice.
Where it comes from
Biosynthetic pathway: Phenylpropanoid pathway — plants build them around a six-carbon aromatic ring.
About the threshold figure
Moderately low. This is part of why clove overwhelms everything placed beside it.
Published thresholds differ by several orders of magnitude, because of differences in measuring method, sample purity and panel. The figure here is an order of magnitude for relative comparison, not a measurement. We give it only for compounds where the literature broadly agrees — 52 of the 106 compounds in the library. The rest are left blank rather than guessed.
Why it sits where it does
A phenol with a free hydroxyl group, forming strong hydrogen bonds, so it boils at around 254 degrees and lasts a very long time.
Where else you meet it
Clove, cassia leaf, holy basil, bay leaf, and Golden Star balm.