Citronellol

Citronellol at a Glance

Citronellol is the acyclic monoterpene alcohol behind the soft rose scent of rose, geranium and citronella oils — the saturated relative of citronellal, and one of the most widely used fragrance materials in perfumery.

It is GRAS as a flavouring, with genuine antimicrobial and anti-Candida activity and established use as an insect repellent, alongside rodent work on anxiolytic and antihypertensive effects.

Chirality

Citronellol is chiral, and nature sorts its two forms by plant family. (S)-(−)-Citronellol is the rose and geranium enantiomer — the soft, delicate rose note — while (R)-(+)-citronellol is the citronella form, made in Cymbopogon by reduction of (R)-(+)-citronellal and carrying a sharper, more citrus-tinged scent. Perfumery treats the two as different materials, and industry makes each on purpose: (S)-(−)-citronellol was the first product of Noyori’s BINAP–ruthenium asymmetric hydrogenation of geraniol, the reaction that helped earn the 2001 Nobel Prize and is still the standard route to the rose enantiomer ^{13Reference 13Takaya H et al. · 2003Asymmetric Hydrogenation of Allylic Alcohols Using BINAP-Ruthenium Complexes: (S)-(−)-Citronellol — synthetic chemistryView study →}, while the (R)-(+) form comes from hydrogenating Takasago’s (R)-citronellal ^{14Reference 14Dylong D et al. · 2025From Turpentine to (-)-Menthol: A New Approach — synthetic chemistryView study →}.

Pharmacologically the split matters less than the scent suggests. The one head-to-head comparison found the two enantiomers equally active against Candida albicans and C. tropicalis — the same MIC and MFC, the same membrane mechanism, the same synergy with amphotericin B ^{8Reference 8Silva DF et al. · 2020Silva DF, et al. (2020). (R)-(+)- and (S)-(-)-β-citronellol in combination with amphotericin B against Candida spp. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/32150884/View study →} — and the rodent antinociception and blood-pressure studies used β-citronellol without stating its form ^{2,3,4Reference 2Brito RG et al. · 2012AnimalCitronellol reduces nociceptive and inflammatory activities in rodentsView study →Reference 3Brito RG et al. · 2013AnimalCitronellol reduces orofacial nociceptive behaviour in mice — involvement of retrosplenial cortex and periaqueductal greyView study →Reference 4Bastos JFA et al. · 2010AnimalHypotensive and vasorelaxant effects of citronellol in ratsView study →}. For the moment, the enantiomer decides what citronellol smells like, not what it does.

What It's Used For

Citronellol is the saturated (dihydro) acyclic monoterpene alcohol behind the soft rose scent of rose, geranium and citronella oils — distinct from citronellal (the corresponding aldehyde, the dominant reactive/repellent compound of citronella oil) and from the unsaturated isomers geraniol (E) and nerol (Z). It has genuine real-world use as an antimicrobial and insect-repellent component, plus rodent anti-inflammatory and blood-pressure-lowering signals — but roughly half the “citronellol” literature is whole-essential-oil work, and there are no human trials of the isolate.

Evidence by IndicationStrength of support · Beta

01Antimicrobial / anti-CandidaShaky42%Isolate + EO in-vitro data with a defined mechanism ^{1,7,8Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →Reference 7Sharma Y et al. · 2020Sharma Y, et al. (2020). β-Citronellol alters cell-surface properties of Candida albicans to influence pathogenicity-related traits. Medical Mycology. https://pubmed.ncbi.nlm.nih.gov/30843057/View study →Reference 8Silva DF et al. · 2020Silva DF, et al. (2020). (R)-(+)- and (S)-(-)-β-citronellol in combination with amphotericin B against Candida spp. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/32150884/View study →}

02Insect repellent / larvicidalShaky38%Registered repellent use + isolate larvicidal/AChE data ^{9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →}

03Anti-inflammatory / antinociceptiveShaky34%Two isolate rodent studies ^{2,3Reference 2Brito RG et al. · 2012AnimalCitronellol reduces nociceptive and inflammatory activities in rodentsView study →Reference 3Brito RG et al. · 2013AnimalCitronellol reduces orofacial nociceptive behaviour in mice — involvement of retrosplenial cortex and periaqueductal greyView study →}

04Antihypertensive / vasorelaxantShaky30%Isolate rodent BP + smooth-muscle data ^{4,5,6Reference 4Bastos JFA et al. · 2010AnimalHypotensive and vasorelaxant effects of citronellol in ratsView study →Reference 5Vasconcelos RP et al. · 2016AnimalVasconcelos RP, et al. (2016). β-Citronellol inhibits the contractility of rat trachea. Brazilian Journal of Medical and Biological Research. https://pubmed.ncbi.nlm.nih.gov/26648088/View study →Reference 6Demirel MA et al. · 2022AnimalGeraniol and β-citronellol participate in the vasorelaxant effects of Rosa damascena oil on rat thoracic aortaView study →}

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Mechanisms

All mechanisms are preclinical; no validated human target.

Pharmacokinetics

No dedicated human pharmacokinetic study of isolated citronellol exists. General terpene-alcohol behavior applies ^{1Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →}: it is highly volatile and lipophilic, well absorbed across skin/mucosa and by inhalation, then rapidly oxidized (allylic/terminal) to citronellic acid and conjugated for urinary excretion, with short biological residence and no meaningful accumulation. Volatility and rapid metabolism are the main dosing constraints — the same limitation that caps geraniol and citral. No isolate bioavailability figures are established.

Clinical Trials

There are no registered or published human clinical trials of isolated citronellol for any indication. Human exposure evidence is limited to food-flavouring intake and cosmetic and fragrance use, including the dermatological patch-test data on which its allergen status rests; every efficacy claim above is essential-oil or preclinical.

Last checked: September 2026.

Isolate vs. Plant Studies

About half of the citronellol literature is whole-oil work, and the two halves are worth keeping apart. The isolate side is respectable: the Candida cell-surface and enantiomer studies dosed pure β-citronellol ^{7,8Reference 7Sharma Y et al. · 2020Sharma Y, et al. (2020). β-Citronellol alters cell-surface properties of Candida albicans to influence pathogenicity-related traits. Medical Mycology. https://pubmed.ncbi.nlm.nih.gov/30843057/View study →Reference 8Silva DF et al. · 2020Silva DF, et al. (2020). (R)-(+)- and (S)-(-)-β-citronellol in combination with amphotericin B against Candida spp. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/32150884/View study →}; the antinociception series ^{2,3Reference 2Brito RG et al. · 2012AnimalCitronellol reduces nociceptive and inflammatory activities in rodentsView study →Reference 3Brito RG et al. · 2013AnimalCitronellol reduces orofacial nociceptive behaviour in mice — involvement of retrosplenial cortex and periaqueductal greyView study →}, the hypotension and tracheal-relaxation studies ^{4,5Reference 4Bastos JFA et al. · 2010AnimalHypotensive and vasorelaxant effects of citronellol in ratsView study →Reference 5Vasconcelos RP et al. · 2016AnimalVasconcelos RP, et al. (2016). β-Citronellol inhibits the contractility of rat trachea. Brazilian Journal of Medical and Biological Research. https://pubmed.ncbi.nlm.nih.gov/26648088/View study →} and the Anopheles larvicidal and acetylcholinesterase work ^{9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →} all used the molecule itself. The rose-oil vasorelaxation study is the exception that proves the rule — it tested the oil, then showed that geraniol and citronellol account for its effect on rat aorta ^{6Reference 6Demirel MA et al. · 2022AnimalGeraniol and β-citronellol participate in the vasorelaxant effects of Rosa damascena oil on rat thoracic aortaView study →}.

The plant side is where the uses come from, and it belongs to the family rather than to citronellol. Rose and geranium oils are citronellol-led but geraniol-rich ^{10,11Reference 10Verma RS et al. · 2011Volatile constituents of essential oil and rose water of damask rose (Rosa damascena Mill.) cultivars from North Indian hills — GC-MS composition studyView study →Reference 11Kačániová M et al. · 2023In vitroAn In-Depth Study on the Chemical Composition and Biological Effects of Pelargonium graveolens Essential Oil — GC-MS composition and in vitro studyView study →}; citronella repellency is a whole-oil result with citronellal as the main active ^{9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →}; and the source oils are described once, on the geraniol page. The honest framing: a modest but genuine isolate pharmacology in animals and in vitro, no human data, and a rose-oil reputation that citronellol shares with its unsaturated parent.

Its Role in Plants

Citronellol is the saturated member of the geraniol family: plants make geraniol from geranyl diphosphate, and reduce its 2,3-double bond to citronellol either directly or by way of citronellal. Rose petals, geranium leaves and citronella grasses each stop at a different point, and each at a different enantiomer.

In geranium, citronellol has a second job — it is the precursor of rose oxide, the sharp green-rose note of Pelargonium and Bulgarian rose oils. Feeding labelled citronellyl diphosphate and citronellyl glucoside to P. graveolens showed both converted into cis- and trans-rose oxide, and that citronellol travels through the plant as its glucoside in the phloem before being freed and cyclised in the leaf ^{15Reference 15Wüst M et al. · 1999AnimalConversion of citronellyl diphosphate and citronellyl beta-D-glucoside into rose oxide by Pelargonium graveolens — plant feeding study, in vivoView study →}. Like its relatives it is a pollinator signal in the flower and a deterrent in the leaf, with antifungal activity against the pathogens a glandular surface meets first ^{1,7Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →Reference 7Sharma Y et al. · 2020Sharma Y, et al. (2020). β-Citronellol alters cell-surface properties of Candida albicans to influence pathogenicity-related traits. Medical Mycology. https://pubmed.ncbi.nlm.nih.gov/30843057/View study →}.

Prevalence in Nature

Citronellol is the leading alcohol of the world’s rose-scented oils and a secondary component of the citronella grasses. Damask rose oil runs 16–35% citronellol beside 8–30% geraniol and 4–10% nerol, the citronellol : geraniol ratio being the grading marker for the oil ^{10Reference 10Verma RS et al. · 2011Volatile constituents of essential oil and rose water of damask rose (Rosa damascena Mill.) cultivars from North Indian hills — GC-MS composition studyView study →}; rose geranium leaf oil is about 30% citronellol with geraniol at half that ^{11Reference 11Kačániová M et al. · 2023In vitroAn In-Depth Study on the Chemical Composition and Biological Effects of Pelargonium graveolens Essential Oil — GC-MS composition and in vitro studyView study →}; Java citronella carries only ~7%, behind citronellal and geraniol ^{12Reference 12Rodrigues KA et al. · 2013In vitroMolluscicidal and larvicidal activities and essential oil composition of Cymbopogon winterianus — GC-MS composition and in vitro bioassayView study →}. It is a minor volatile of catnip, lemongrass, lemon balm and many Lamiaceae, and of the fruit and wine aroma literature, where it contributes to the “rose” descriptor of some grape varieties. As always, the figures are shares of the oil, and rose oil in particular shifts with cultivar, flower stage and growing site ^{10Reference 10Verma RS et al. · 2011Volatile constituents of essential oil and rose water of damask rose (Rosa damascena Mill.) cultivars from North Indian hills — GC-MS composition studyView study →}.

Major Natural Sources

Source	Plant part	Reported citronellol content
Damask rose (Rosa × damascena)	flower oil	15.9–35.3%, (S)-(−) 10Reference 10Verma RS et al. · 2011Volatile constituents of essential oil and rose water of damask rose (Rosa damascena Mill.) cultivars from North Indian hills — GC-MS composition studyView study →
Rose geranium (Pelargonium graveolens)	leaf oil	~29.7%, (S)-(−) 11Reference 11Kačániová M et al. · 2023In vitroAn In-Depth Study on the Chemical Composition and Biological Effects of Pelargonium graveolens Essential Oil — GC-MS composition and in vitro studyView study →
Java citronella (Cymbopogon winterianus)	leaf oil	~7.3%, (R)-(+) 12Reference 12Rodrigues KA et al. · 2013In vitroMolluscicidal and larvicidal activities and essential oil composition of Cymbopogon winterianus — GC-MS composition and in vitro bioassayView study →

Ceylon citronella (Cymbopogon nardus) and the rose-scented Pelargonium cultivars carry it in comparable proportions; see the family’s source-oil account on the geraniol page.

Other Reported Sources

• Catnip — a minor volatile beside nepetalactone
• Lemongrass and lemon balm — trace, behind citral and citronellal
• Bulgarian and Turkish rose oils — the classical (S)-(−) sources
• Muscat-type grapes and wines — a varietal aroma contributor

Discovery & Synthesis

Citronellol was characterised in the late nineteenth century, in the same programme that fixed the structures of geraniol, citral and citronellal, as the dihydro relative of geraniol found in both citronella and rose oils; the name came from the former, the commercial importance from the latter. Its modern history is a landmark of catalysis: in 1987 Noyori’s group showed that a BINAP–ruthenium complex hydrogenates geraniol to (S)-(−)-citronellol in essentially complete enantiomeric excess, and Takasago ran the process at scale — the first industrial asymmetric hydrogenation of an allylic alcohol ^{13Reference 13Takaya H et al. · 2003Asymmetric Hydrogenation of Allylic Alcohols Using BINAP-Ruthenium Complexes: (S)-(−)-Citronellol — synthetic chemistryView study →}.

Manufacture today is by hydrogenation: of geraniol or nerol (both made from myrcene) to racemic or, with a chiral catalyst, single-enantiomer citronellol; or of (R)-citronellal from the Takasago menthol chain to (R)-(+)-citronellol ^{13,14Reference 13Takaya H et al. · 2003Asymmetric Hydrogenation of Allylic Alcohols Using BINAP-Ruthenium Complexes: (S)-(−)-Citronellol — synthetic chemistryView study →Reference 14Dylong D et al. · 2025From Turpentine to (-)-Menthol: A New Approach — synthetic chemistryView study →}. Natural citronellol is still distilled from rose, geranium and citronella oils for natural-label fragrance, but as with geraniol it is a small share of supply.

Patents: not yet researched.

Commercial Production

Citronellol is one of the highest-volume rose materials in perfumery, used in soaps, detergents and fine fragrance in both the racemic and the (S)-(−) grade, and is the parent of rose oxide, citronellyl acetate and hydroxycitronellal. It is also a registered active in plant-based insect repellents, where its short residence on skin — the same volatility that makes it a top note — limits protection time unless it is fixed ^{9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →}.

Toxicity & Safety

Citronellol’s toxicity is low and its food use uncontroversial; the whole safety story is skin sensitization, which is why the EU requires it to be named on cosmetic labels.

Safety at a Glance

✅ Low / no toxicityAllergy risk

• Low acute toxicity. A GRAS flavoring substance with a long history of trace-level food use and a favorable general-toxicology review.
• Established human contact allergen. A recognized skin sensitizer, and an EU fragrance allergen that must be declared on cosmetic labels.
• Aged oil is worse. Autoxidized or poorly stored material sensitizes more than the fresh compound — prefer fresh, properly diluted preparations.
• Already sensitized? Avoid it. There is no safe re-exposure level once contact allergy is established.

Full Safety & Interactions Detail

Citronellol has low acute toxicity — a GRAS flavoring substance with a long history of food use at trace levels and a favorable general-toxicology profile summarized in a 2019 systematic review ^{1Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →}.

The headline safety point is topical: citronellol is an established human contact allergen and is on the EU list of fragrance allergens that must be declared on cosmetic labels (Cosmetics Regulation 1223/2009, Annex III). It is a recognized skin sensitizer, and — as with other monoterpene alcohols — autoxidized (aged or poorly stored) material is more sensitizing than the fresh compound: on air exposure citronellol forms hydroperoxides and a hydroxyhydroperoxide that are stronger sensitisers than the parent, the terpene’s single double bond steering it down a path closer to linalool’s than to geraniol’s ^{16Reference 16Rudbäck J et al. · 2014AnimalCharacterization of skin sensitizers from autoxidized citronellol - impact of the terpene structure on the autoxidation process — chemical analysis and mouse local lymph node assay, animal modelView study →}.

In practice, prefer fresh, properly diluted preparations for topical use, and sensitized individuals should avoid it. No human or reproductive-toxicity data exist for isolated citronellol. Dietary flavouring levels and normal cosmetic exposure are long-standing; therapeutic or concentrated essential-oil exposure has not been studied.

Dosage

There is no established therapeutic or supplemental dose for isolated citronellol and no human dosing exists. All figures in the literature are food-additive reference levels (trace flavoring) or research doses in rodents/in-vitro, not recommendations. For topical/aromatherapy use it appears as a minor essential-oil constituent, where dilution and freshness matter more than a target dose (see Safety).

These are doses studied in research and are not a personal recommendation.

References

1. Santos WBR, et al. (2019). Citronellol, a monoterpene alcohol with promising pharmacological activities — a systematic review. Food and Chemical Toxicology. https://pubmed.ncbi.nlm.nih.gov/30453001/
2. Brito RG, et al. (2012). Citronellol reduces nociceptive and inflammatory activities in rodents. Journal of Natural Medicines. https://pubmed.ncbi.nlm.nih.gov/22350215/
3. Brito RG, et al. (2013). Citronellol reduces orofacial nociceptive behaviour in mice — involvement of retrosplenial cortex and periaqueductal grey. Basic & Clinical Pharmacology & Toxicology. https://pubmed.ncbi.nlm.nih.gov/23035741/
4. Bastos JFA, et al. (2010). Hypotensive and vasorelaxant effects of citronellol in rats. Basic & Clinical Pharmacology & Toxicology. https://pubmed.ncbi.nlm.nih.gov/20002067/
5. Vasconcelos RP, et al. (2016). β-Citronellol inhibits the contractility of rat trachea. Brazilian Journal of Medical and Biological Research. https://pubmed.ncbi.nlm.nih.gov/26648088/
6. Demirel MA, et al. (2022). Geraniol and β-citronellol participate in the vasorelaxant effects of Rosa damascena oil on rat thoracic aorta. Fitoterapia. https://pubmed.ncbi.nlm.nih.gov/35728707/
7. Sharma Y, et al. (2020). β-Citronellol alters cell-surface properties of Candida albicans to influence pathogenicity-related traits. Medical Mycology. https://pubmed.ncbi.nlm.nih.gov/30843057/
8. Silva DF, et al. (2020). (R)-(+)- and (S)-(-)-β-citronellol in combination with amphotericin B against Candida spp. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/32150884/
9. Tang X, et al. (2024). Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensis. Parasitology Research. https://pubmed.ncbi.nlm.nih.gov/39227462/
10. Verma RS, Padalia RC, Chauhan A, et al. (2011). Volatile constituents of essential oil and rose water of damask rose (Rosa damascena Mill.) cultivars from North Indian hills — GC-MS composition study. Nat Prod Res. https://pubmed.ncbi.nlm.nih.gov/21711177/
11. Kačániová M, Vukic M, Vukovic NL, et al. (2023). An In-Depth Study on the Chemical Composition and Biological Effects of Pelargonium graveolens Essential Oil — GC-MS composition and in vitro study. Foods. https://pubmed.ncbi.nlm.nih.gov/38201061/
12. Rodrigues KA, Dias CN, do Amaral FM, et al. (2013). Molluscicidal and larvicidal activities and essential oil composition of Cymbopogon winterianus — GC-MS composition and in vitro bioassay. Pharm Biol. https://pubmed.ncbi.nlm.nih.gov/23855832/
13. Takaya H, Ohta T, Inoue S, et al. (2003). Asymmetric Hydrogenation of Allylic Alcohols Using BINAP-Ruthenium Complexes: (S)-(−)-Citronellol — synthetic chemistry. Organic Syntheses. https://doi.org/10.1002/0471264180.os072.10
14. Dylong D, Panten J, Rußbüldt B, et al. (2025). From Turpentine to (-)-Menthol: A New Approach — synthetic chemistry. ChemSusChem. https://pubmed.ncbi.nlm.nih.gov/40552362/
15. Wüst M, Beck T, Mosandl A (1999). Conversion of citronellyl diphosphate and citronellyl beta-D-glucoside into rose oxide by Pelargonium graveolens — plant feeding study, in vivo. J Agric Food Chem. https://pubmed.ncbi.nlm.nih.gov/10564036/
16. Rudbäck J, Hagvall L, Börje A, et al. (2014). Characterization of skin sensitizers from autoxidized citronellol - impact of the terpene structure on the autoxidation process — chemical analysis and mouse local lymph node assay, animal model. Contact Dermatitis. https://pubmed.ncbi.nlm.nih.gov/24673435/

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