The Sunlight Experiment

Compound Monograph

Citronellol

Citronellol is the saturated acyclic monoterpene alcohol behind the soft rose scent of rose, geranium and citronella oils — a GRAS flavour/fragrance ingredient with real antimicrobial, anti-Candida and insect-repellent use and rodent anti-inflammatory and blood-pressure-lowering signals. Distinct from its aldehyde (citronellal) and its unsaturated isomers (geraniol/nerol); an EU-labelled skin sensitiser with no human trials of the isolate.

Work in progress

Classification

Citronellol is a monoterpene alcohol (monoterpenoid), part of the terpenoids class. The largest class of plant compounds, built from five-carbon isoprene units — the essential-oil aromatics, resins, bitter principles, saponins, and plant sterols.

Terpenoids Monoterpenes

Where Does It Come From? (6)

Citronellol is a naturally occurring monoterpene alcohol (monoterpenoid), found in Rose, Rose geranium, Citronella grass and 3 other sources. It is well tolerated orally (low toxicity).

Catnip Nepeta cataria CitronellaCitronella grassGeraniumRoseRose geranium

Pharmacology & Research

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.

What the evidence supports
  • Antimicrobial/anti-Candida and repellent use are real: isolate activity against Candida with amphotericin-B synergy, and larvicidal/AChE activity, though much field efficacy belongs to whole citronella oil 7,8,9Reference 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 →Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →.
  • The honest headline: anti-inflammatory and antihypertensive effects are rodent-only at high doses; the headline safety issue is topical — it is an EU-declarable skin sensitiser, worse when oxidised 1Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →.
Evidence by indicationStrength of support
Antimicrobial / Anti-CandidaShaky
42%
Insect Repellent / LarvicidalShaky
38%
Anti-Inflammatory / AntinociceptiveShaky
34%
Antihypertensive / VasorelaxantShaky
30%
1. Antimicrobial / anti-Candida

β-Citronellol alters Candida albicans cell-surface hydrophobicity, adhesion and hyphal/pathogenicity traits 7Reference 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 → and shows synergy with amphotericin B against Candida spp. 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 →, with a lipophilic membrane-partitioning mechanism reviewed across the literature 1Reference 1Santos WBR et al. · 2019Systematic reviewCitronellol, a monoterpene alcohol with promising pharmacological activities — a systematic reviewView study →.

Gap: MICs are moderate versus dedicated antifungals; almost all data are in-vitro with no infection-model or clinical confirmation, and much activity is reported for whole oils rather than the isolate 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 →.

2. Insect repellent / larvicidal

Citronellol is a component of registered plant-based repellents and, as an isolate, shows larvicidal activity and acetylcholinesterase inhibition against Anopheles mosquitoes 9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →.

Gap: free citronellol is volatile and short-acting — repellency is real but brief without fixatives, and most field efficacy belongs to whole citronella oil, not the pure alcohol 9Reference 9Tang X et al. · 2024Lemongrass essential oil and its major component citronellol: larvicidal activity and acetylcholinesterase inhibition against Anopheles sinensisView study →.

3. Anti-inflammatory / antinociceptive

Systemic β-citronellol reduced nociceptive and inflammatory behaviour in rodents 2Reference 2Brito RG et al. · 2012AnimalCitronellol reduces nociceptive and inflammatory activities in rodentsView study → and reduced orofacial nociception with evidence of periaqueductal-grey / retrosplenial-cortex involvement 3Reference 3Brito RG et al. · 2013AnimalCitronellol reduces orofacial nociceptive behaviour in mice — involvement of retrosplenial cortex and periaqueductal greyView study →.

Gap: rodent behavioural endpoints only, at supraphysiological doses, with inferred (not receptor-resolved) mechanism and no human data 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 →.

4. Antihypertensive / vasorelaxant

Intravenous citronellol produced dose-dependent hypotension and vasorelaxation in rats 4Reference 4Bastos JFA et al. · 2010AnimalHypotensive and vasorelaxant effects of citronellol in ratsView study →, and β-citronellol relaxed rat tracheal 5Reference 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 aortic 6Reference 6Demirel MA et al. · 2022AnimalGeraniol and β-citronellol participate in the vasorelaxant effects of Rosa damascena oil on rat thoracic aortaView study → smooth muscle.

Gap: acute anaesthetised-rodent / isolated-tissue models only, endothelium-independent at high doses, with no chronic dosing, no oral route and no human relevance established 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 →.

Mechanisms

Target / pathwayEffectRelevant to
Microbial lipid membrane (lipophilic partition)↑ permeability, leakage, loss of integrityantimicrobial / antifungal
Candida cell surface (hydrophobicity, adhesion, hyphae)↓ adhesion/virulence; amphotericin-B synergyanti-Candida
Peripheral + central nociceptive pathways (PAG, retrosplenial cortex)reduced nociceptive/inflammatory behaviourantinociceptive / anti-inflammatory
Vascular / airway smooth muscle (endothelium-independent)relaxation → hypotension/vasodilationantihypertensive / vasorelaxant
Insect acetylcholinesteraseenzyme inhibitionlarvicidal / insecticidal

All mechanisms are preclinical; no validated human target.

Pharmacokinetics

No dedicated human pharmacokinetic study of isolated citronellol exists. General terpene-alcohol behaviour 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 oxidised (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/fragrance use (including dermatological patch-test data); all efficacy claims above are essential-oil or preclinical.

CompletedPlannedTerminatedPreclinical
—(none)——Modest

Last checked: July 2026.

Toxicity & Safety

Citronellol has low acute toxicity — a GRAS flavouring substance with a long history of food use at trace levels and a favourable general-toxicology profile summarised 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 recognised skin sensitiser, and — as with other monoterpene alcohols — autoxidised (aged or poorly stored) material is more sensitising than the fresh compound. In practice, prefer fresh, properly diluted preparations for topical use, and sensitised individuals should avoid it.

Pregnancy & lactation

Dietary/cosmetic amounts fine; caution with concentrated use. No isolate human or reproductive-toxicity data exist. Dietary/flavouring-level and normal cosmetic exposure is not considered a concern, but for therapeutic or concentrated essential-oil use there is insufficient evidence to establish safety — standard aromatherapy caution applies (avoid ingesting concentrated oils and undiluted topical use in pregnancy and lactation).

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 flavouring) 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).

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/