Compounds · Alcohols · Terpenoid pathway
Citronellol
Also known as β-Citronellol · Cephrol — an analysis may use any of these names
Rose, soft, less harsh than geraniol. The same direction of smell, spoken more quietly.
- CAS
- 106-22-9
- Formula
- C10H20O
- Molar mass
- 156.27
- Odour threshold
- 40 ppbin water
- Boiling point
- ≈ 225 °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: CITRONELLOL.
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: Terpenoid pathway — plants build them from identical five-carbon blocks.
About the threshold figure
Moderate, at the same level as geraniol. The two almost always occur together.
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
The alcohol corresponding to citronellal; its extra hydroxyl group makes it boil nearly twenty degrees higher and stay considerably longer.
Where else you meet it
Rose, geranium, lemongrass. One of the allergens that must be declared individually on cosmetic labels in the European Union.