Geraniol

Geraniol at a Glance

Geraniol is an acyclic monoterpene alcohol and the signature rose and geranium aroma compound, also abundant in palmarosa and citronella oils.

It is one of the better-studied dietary monoterpenes preclinically — covering anticancer, anti-inflammatory and antimicrobial activity — and it is a genuine insect repellent with commercial use, not merely a folk one.

It is GRAS as a flavour and fragrance ingredient.

The Geraniol Family

Geraniol is the parent of a small family of C10 molecules that share a skeleton, share the same plants, and are constantly confused in the literature. Most “geraniol” figures in herb monographs turn out, on inspection, to be one of its relatives.

Molecule	Relationship to geraniol	Where it dominates
Geraniol	the trans (E) allylic alcohol	palmarosa, rose, geranium
Nerol	the cis (Z) isomer — same formula, the other geometry at the 2,3-double bond	rose and neroli (minor)
Citronellol	the saturated (dihydro) alcohol; chiral, (−) in citronella, (+) in rose and geranium	rose, geranium, citronella
Citronellal	the aldehyde of citronellol	citronella, lemon eucalyptus
Geranial + neral = citral	the aldehydes of geraniol and nerol, always together	lemongrass, lemon myrtle
Geranyl acetate	the acetate ester	Mexican tarragon, some citrus and Cymbopogon oils
Geranic acid	the oxidation product and main metabolite	not a plant marker; what the body makes of geraniol 4,5Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →Reference 5Jäger T et al. · 2023Clinical trialHuman Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteersView study →

Three consequences follow. The oil that carries “geraniol” is often really the ester or the aldehyde — Mexican tarragon oil is about half geranyl acetate and only ~8% free geraniol ^{15Reference 15Hernandez-Leon A et al. · 2020AnimalRole of β-Caryophyllene in the Antinociceptive and Anti-Inflammatory Effects of Tagetes lucida CavView study →}; lemongrass is citral, with geraniol at ~3% ^{16Reference 16Ekpenyong CE et al. · 2015ReviewEthnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts — reviewView study →}. The family interconverts, in the plant and in the reactor: industry reaches citronellol, citronellal and citral from geraniol and its parent myrcene ^{21,22Reference 21Behr A · 2009ReviewMyrcene as a natural base chemical in sustainable chemistry: a critical review — reviewView study →Reference 22Surendran S et al. · 2021ReviewMyrcene-What Are the Potential Health Benefits of This Flavouring and Aroma Agent? — reviewView study →}. And a finding on one member does not belong to another — citronellol’s rose-oil pharmacology and citronellal’s repellency are their own pages.

Rose, Geranium, Palmarosa & Citronella

The family’s four defining oils, described once here; the sibling pages point back.

Rose oil (Rosa × damascena) is a citronellol–geraniol–nerol oil with a long-chain hydrocarbon tail. Indian cultivar oils ran citronellol 15.9–35.3%, geraniol 8.3–30.2% and nerol 4.0–9.6%, with linalool under 3% and the alkanes nonadecane and heneicosane making up much of the rest ^{12Reference 12Verma 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 →}. The citronellol : geraniol ratio is the industry’s grading marker for rose oil — the balance shifts with cultivar, flower stage and site — and rose water is a different material again, dominated by 2-phenylethanol with only 3–7% geraniol ^{12Reference 12Verma 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) is rose’s understudy: a leaf oil dominated by citronellol (~30%) with geraniol second (~15%), the source of most “geranium” fragrance and the reason the two plants are so often confused ^{13Reference 13Kačániová 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 →}.

Palmarosa (Cymbopogon martinii) is the geraniol oil — geraniol is its major constituent by a wide margin — and the “Indian geranium oil” from which the molecule was first isolated ^{14Reference 14Mahant S et al. · 2021In vitroInsights into the mechanism of Cymbopogan martinii essential oil in topical therapy of acne vulgaris — GC-MS composition and in vitro studyView study →}. It is the natural source of choice where geraniol itself, rather than a rose note, is wanted.

Citronella (Cymbopogon nardus and C. winterianus) belongs to the aldehyde and saturated-alcohol end of the family — citronellal first, then geraniol and citronellol — which is why its repellency literature sits on the citronellal page rather than here, while the isolated-geraniol repellent data are geraniol’s own ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}.

The HMG-CoA Question

For twenty years the standard explanation of geraniol’s chemopreventive activity was that it, like other dietary isoprenoids, suppresses HMG-CoA reductase and so starves tumour cells of mevalonate-pathway intermediates. Geraniol does inhibit the enzyme. But in MCF-7 breast-cancer cells the antiproliferative effect — G1 arrest, loss of cyclin D1, E and A, and inhibition of CDK2 — could not be rescued by adding mevalonate, which it should have been if mevalonate starvation were the cause ^{3Reference 3Duncan RE et al. · 2004Geraniol and β-ionone inhibit proliferation, cell-cycle progression and CDK2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activityView study →}. The two effects co-occur but one does not explain the other. The Anticancer score below is set on that basis: a large preclinical literature with a signature mechanism that is correlative, not causal, and no human oncology data ^{2,3Reference 2Cho M et al. · 2016ReviewThe antitumour effects of geraniol: modulation of cancer hallmark pathways (review)View study →Reference 3Duncan RE et al. · 2004Geraniol and β-ionone inhibit proliferation, cell-cycle progression and CDK2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activityView study →}.

What It's Used For

Geraniol is an acyclic monoterpene alcohol with a sweet, rose-like odor — the signature aroma of rose, geranium and palmarosa, and a high-volume flavor and fragrance ingredient. Two framing points. First, keep it distinct from its close relatives: geraniol is the trans (E) alcohol, while nerol is its cis isomer, citronellol the saturated analogue, geranial the aldehyde (part of citral) and geranyl acetate the ester — several source-herb notes actually report the ester, not free geraniol. Second, although geraniol is one of the better-studied dietary monoterpenes in preclinical chemoprevention, its human evidence is a single indication (IBS) and its pharmacokinetics are limiting — rapid oxidation to geranic acid, short residence, high volatility ^{4,5Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →Reference 5Jäger T et al. · 2023Clinical trialHuman Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteersView study →}.

Its most robust isolate data are antimicrobial/antifungal (a defined ergosterol-and-membrane mechanism) ^{9Reference 9Pereira Fde O et al. · 2015Antifungal activity of geraniol and citronellol against Trichophyton rubrum involves inhibition of ergosterol biosynthesisView study →} and a genuine role as an insect repellent ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}.

Evidence by IndicationStrength of support · Beta

01Antimicrobial / antifungalShaky44%Broad in-vitro + defined mechanism ^{9,1Reference 9Pereira Fde O et al. · 2015Antifungal activity of geraniol and citronellol against Trichophyton rubrum involves inhibition of ergosterol biosynthesisView study →Reference 1Mączka W et al. · 2020One hundred faces of geraniolView study →}

02Irritable bowel syndromeShaky40%One placebo-controlled RCT (specific formulation) ^{11Reference 11Ricci C et al. · 2022RCTGeraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial — randomised controlled trialView study →}

03Anti-inflammatoryShaky34%Rodent colitis models with pathway data ^{6,7Reference 6Medicherla K et al. · 2015AnimalOral administration of geraniol ameliorates acute experimental murine colitis by inhibiting pro-inflammatory cytokines and NF-κB signallingView study →Reference 7Soubh AA et al. · 2015Geraniol ameliorates TNBS-induced colitis: involvement of Wnt/β-catenin, p38 MAPK, NF-κB and PPARγ signalling pathwaysView study →}

04Anticancer (chemoprevention)Shaky30%Large preclinical body, mechanism disputed ^{2,3Reference 2Cho M et al. · 2016ReviewThe antitumour effects of geraniol: modulation of cancer hallmark pathways (review)View study →Reference 3Duncan RE et al. · 2004Geraniol and β-ionone inhibit proliferation, cell-cycle progression and CDK2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activityView study →}

05Metabolic / antidiabeticShaky22%Rodent models only ^{8Reference 8Babukumar S et al. · 2017AnimalGeraniol ameliorates hyperglycemia by attenuating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic ratsView study →}

06Insect repellent (use)Shaky30%Field/semi-field efficacy ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}

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Mechanisms

Pharmacokinetics

Geraniol is rapidly absorbed and rapidly cleared: in rats, whole-blood decline follows pseudo-first-order kinetics with a half-life of roughly 12.5 minutes after IV dosing ^{4Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →}. It is metabolized by allylic oxidation to acidic products — chiefly geranic acid, plus 8-carboxygeraniol, 3-hydroxycitronellic acid and Hildebrandt acid ^{4Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →}. Human data confirm this: after oral dosing, urinary metabolites are dominated by Hildebrandt acid (~34% of dose) and geranic acid (~13%), with metabolite half-lives of ~2–4 hours ^{5Reference 5Jäger T et al. · 2023Clinical trialHuman Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteersView study →}. The net picture — short residence, extensive first-pass oxidation and conjugation, low sustained systemic exposure, compounded by high volatility — is the central caveat separating isolated-geraniol pharmacology from the high-dose preclinical results, and it is why the one oral clinical trial used a low-absorbable, sustained-delivery formulation.

Clinical Trials

Human data on isolated geraniol are essentially one endpoint: the IBS trial, a double-blind randomised comparison of a low-absorbable geraniol supplement against placebo in 56 patients over four weeks ^{11Reference 11Ricci C et al. · 2022RCTGeraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial — randomised controlled trialView study →}. No trial for the anticancer, antidiabetic or anti-inflammatory applications is registered or published, and no further geraniol trial is listed; the nearest registry entry is a geranium-oil aromatherapy study, which is a whole oil. Human exposure studies exist for metabolism and excretion only ^{5Reference 5Jäger T et al. · 2023Clinical trialHuman Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteersView study →}.

Last checked: September 2026.

Isolate vs. Plant Studies

Geraniol is one of the few monoterpenes whose human evidence is the isolate, and that is a strength: the IBS trial dosed geraniol itself, in a formulation designed to keep it in the gut ^{11Reference 11Ricci C et al. · 2022RCTGeraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial — randomised controlled trialView study →}, and the human metabolism study dosed pure geraniol ^{5Reference 5Jäger T et al. · 2023Clinical trialHuman Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteersView study →}. The preclinical base is likewise almost all the pure molecule — the colitis models ^{6,7Reference 6Medicherla K et al. · 2015AnimalOral administration of geraniol ameliorates acute experimental murine colitis by inhibiting pro-inflammatory cytokines and NF-κB signallingView study →Reference 7Soubh AA et al. · 2015Geraniol ameliorates TNBS-induced colitis: involvement of Wnt/β-catenin, p38 MAPK, NF-κB and PPARγ signalling pathwaysView study →}, the diabetic rats ^{8Reference 8Babukumar S et al. · 2017AnimalGeraniol ameliorates hyperglycemia by attenuating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic ratsView study →}, the ergosterol mechanism ^{9Reference 9Pereira Fde O et al. · 2015Antifungal activity of geraniol and citronellol against Trichophyton rubrum involves inhibition of ergosterol biosynthesisView study →}, the MCF-7 work ^{3Reference 3Duncan RE et al. · 2004Geraniol and β-ionone inhibit proliferation, cell-cycle progression and CDK2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activityView study →} and the repellency field trials ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}.

What the plant evidence cannot do is stand in for it. Rose, geranium and palmarosa oils are citronellol–geraniol mixtures in which citronellol often leads ^{12,13Reference 12Verma 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 13Kačániová 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 →}; rose oil’s clinical and aromatherapy literature is rose’s, and its main alcohol is not geraniol. The one place plant data are relevant here is repellency, where geraniol-rich oils and pure geraniol have both been tested and the isolate performs at least as well ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}. Everywhere else, the honest framing is the reverse of the usual: strong isolate data, weak plant data, and no reason to expect a rose product to reproduce a geraniol result.

Its Role in Plants

Geraniol is the simplest product of the monoterpene pathway — geranyl diphosphate with its diphosphate removed — and plants make it in two quite different ways. The classical route is a geraniol synthase, a terpene synthase; in Madagascar periwinkle that enzyme, in the plastid, opens the monoterpenoid branch that leads through iridoids to the anticancer alkaloids vinblastine and vincristine ^{19Reference 19Simkin AJ et al. · 2013In vitroCharacterization of the plastidial geraniol synthase from Madagascar periwinkle which initiates the monoterpenoid branch of the alkaloid pathway in internal phloem associated parenchyma — enzyme characterisation, in vitroView study →}. Geraniol is thus the C10 gateway to the whole secoiridoid and monoterpene-indole-alkaloid world, from catnip’s nepetalactone to gentian’s bitters.

Roses do it differently. Rose petals make geraniol with a Nudix hydrolase, RhNUDX1, a cytosolic enzyme from a family better known for housekeeping, which dephosphorylates geranyl diphosphate in a step no terpene synthase performs ^{17Reference 17Magnard JL et al. · 2015In vitroPLANT VOLATILESView study →}; the gene was duplicated and specialised within the Rosaceae, which is why scented roses have it and their relatives largely do not ^{18Reference 18Conart C et al. · 2022Duplication and Specialization of NUDX1 in Rosaceae Led to Geraniol Production in Rose Petals — plant genomics studyView study →}. It is one of the clearest cases of a plant evolving an entirely new route to an old molecule.

Once made, geraniol is a pollinator signal — the rose note itself — and a defence: it repels mosquitoes and other insects ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →} and is antifungal against the pathogens that attack leaves and fruit ^{9Reference 9Pereira Fde O et al. · 2015Antifungal activity of geraniol and citronellol against Trichophyton rubrum involves inhibition of ergosterol biosynthesisView study →}. Where roses release it to attract, palmarosa and citronella accumulate it to deter.

Prevalence in Nature

Geraniol is one of the most widespread plant volatiles, present at trace levels in hundreds of species and dominant in a handful ^{1Reference 1Mączka W et al. · 2020One hundred faces of geraniolView study →}. The rich sources are the Poaceae (palmarosa, where it is the major constituent ^{14Reference 14Mahant S et al. · 2021In vitroInsights into the mechanism of Cymbopogan martinii essential oil in topical therapy of acne vulgaris — GC-MS composition and in vitro studyView study →}; citronella; lemongrass at ~3% ^{16Reference 16Ekpenyong CE et al. · 2015ReviewEthnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts — reviewView study →}), the Rosaceae (damask rose, 8–30% of the oil ^{12Reference 12Verma 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 →}) and the Geraniaceae (rose geranium, ~15% ^{13Reference 13Kačániová 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 →}); it defines a geraniol chemotype of thyme and appears in Mexican tarragon (~8%, beside far more geranyl acetate) ^{15Reference 15Hernandez-Leon A et al. · 2020AnimalRole of β-Caryophyllene in the Antinociceptive and Anti-Inflammatory Effects of Tagetes lucida CavView study →}, catnip, rosewood (~1%) and many Lamiaceae. As with every terpene, the figures are shares of the essential oil, and they move with cultivar, plant part, flowering stage and distillation ^{12Reference 12Verma 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 geraniol content
Palmarosa (Cymbopogon martinii)	leaf oil	the major constituent 14Reference 14Mahant S et al. · 2021In vitroInsights into the mechanism of Cymbopogan martinii essential oil in topical therapy of acne vulgaris — GC-MS composition and in vitro studyView study →
Damask rose (Rosa × damascena)	flower oil	8.3–30.2% (citronellol 16–35%, nerol 4–10%) 12Reference 12Verma 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	~14.6% (citronellol ~30%) 13Reference 13Kačániová 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 →
Mexican tarragon (Tagetes lucida)	aerial-parts oil	~8% (geranyl acetate ~50%) 15Reference 15Hernandez-Leon A et al. · 2020AnimalRole of β-Caryophyllene in the Antinociceptive and Anti-Inflammatory Effects of Tagetes lucida CavView study →
Lemongrass (Cymbopogon citratus)	leaf oil	~3% (citral 65–85%) 16Reference 16Ekpenyong CE et al. · 2015ReviewEthnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts — reviewView study →

Citronella oils carry geraniol as a secondary component behind citronellal; see citronellal.

Other Reported Sources

• Catnip — with nepetalactone, its iridoid descendant
• Thyme — the geraniol chemotype
• Rosewood — ~1% beside linalool
• Neroli and bitter-orange flower oils, with nerol
• Coriander, lemon balm, lemon myrtle and other citral-type oils, as a minor alcohol ^{1Reference 1Mączka W et al. · 2020One hundred faces of geraniolView study →}

Discovery & Synthesis

Geraniol was isolated in 1871 by the German chemist Oscar Jacobsen from the Indian grass oil then sold as “geranium oil” — palmarosa — and named for the fragrance rather than the plant; the true geraniums acquired the compound’s name second-hand. Its constitution as an acyclic dimethyloctadienol was worked out in the following decades, in the same programme that gave chemistry citral, linalool and the isoprene rule; the cis isomer was separated and named nerol from neroli oil.

Manufacture today is synthetic. Geraniol is one of the fragrance industry’s highest-tonnage alcohols and is made from myrcene — itself produced by pyrolysing β-pinene from turpentine — by hydrochlorination to geranyl chloride and conversion to the acetate and the alcohol ^{21,22Reference 21Behr A · 2009ReviewMyrcene as a natural base chemical in sustainable chemistry: a critical review — reviewView study →Reference 22Surendran S et al. · 2021ReviewMyrcene-What Are the Potential Health Benefits of This Flavouring and Aroma Agent? — reviewView study →}, and from citral by selective hydrogenation. Natural geraniol is still distilled from palmarosa where a botanical label is wanted, but it is a small fraction of supply.

Patents: not yet researched.

Commercial Production

Geraniol is a bulk aroma chemical and an intermediate. It gives the rose note to soaps, detergents and fine fragrance, is a common flavour in fruit and floral profiles, and is the starting material for citronellol (by hydrogenation), citronellal and citral (by oxidation), and their esters ^{21,22Reference 21Behr A · 2009ReviewMyrcene as a natural base chemical in sustainable chemistry: a critical review — reviewView study →Reference 22Surendran S et al. · 2021ReviewMyrcene-What Are the Potential Health Benefits of This Flavouring and Aroma Agent? — reviewView study →}. Its second commercial life is as a registered insect repellent and biopesticide active, formulated at around 5% in sprays, candles and diffusers ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}. Both careers run into the same limit: geraniol is volatile, and a scent or a repellent effect that lasts is a formulation problem.

Toxicity & Safety

Geraniol is an FDA/FEMA GRAS flavoring with a favorable systemic-toxicity profile — a JECFA group ADI of 0.5 mg/kg body weight/day and rodent NOAELs well above 200 mg/kg — so ingestion toxicity at flavoring levels is low. The headline safety issue is topical, not systemic: geraniol is a recognized fragrance contact allergen and one of the 26 fragrance allergens requiring individual EU labeling, causing allergic contact dermatitis in sensitized individuals. Critically, auto-oxidation on exposure to air, heat or light generates hydroperoxides that are markedly more sensitizing than fresh geraniol — so aged essential oils carry more allergenic risk. Undiluted material also irritates skin and mucosa. Interactions are theoretical only: geraniol modulates hepatic xenobiotic-metabolizing and antioxidant enzymes in rodents at high doses ^{4Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →}, a mechanistic basis for possible CYP interactions, with none documented at food or fragrance levels.

Oxidised Geraniol & Contact Allergy

Fresh geraniol is a weak sensitiser; air-exposed geraniol is a moderate one. On autoxidation it follows a different route from linalool and limonene, which form hydroperoxides as their primary products: geraniol gives hydrogen peroxide together with the aldehydes geranial and neral, formed through a hydroxyhydroperoxide, plus a smaller amount of a linalool-type hydroperoxide ^{20Reference 20Hagvall L et al. · 2007AnimalFragrance compound geraniol forms contact allergens on air exposureView study →}. In the local lymph node assay the oxidised mixture sensitised markedly more than the parent, and the aldehydes carry much of that potency ^{20Reference 20Hagvall L et al. · 2007AnimalFragrance compound geraniol forms contact allergens on air exposureView study →}. The practical reading is the same as for the other fragrance terpenes: what sits in an old, opened bottle is not the molecule that was put in it, so keep geraniol-rich oils cool, dark and sealed, and dilute them on skin.

Safety at a Glance

✅ Low / no toxicity

• GRAS by ingestion. A JECFA group ADI of 0.5 mg/kg/day and rodent NOAELs well above 200 mg/kg; dietary and flavouring exposure is low-risk.
• A labelled fragrance allergen. One of the 26 fragrance substances the EU requires to be named on cosmetics; causes allergic contact dermatitis in sensitised people.
• Oxidised geraniol is worse. Air exposure forms geranial, neral and hydrogen peroxide with a higher sensitising potency than fresh geraniol ^{20Reference 20Hagvall L et al. · 2007AnimalFragrance compound geraniol forms contact allergens on air exposureView study →}. Old or repeatedly opened oils are the risk.
• Undiluted material irritates skin and mucosa; repellent and fragrance formulations are diluted for that reason ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}.
• Interactions are theoretical. High-dose rodent modulation of hepatic xenobiotic-metabolising enzymes ^{4Reference 4Pavan B et al. · 2018Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymesView study →}; nothing documented at food or fragrance exposure.

Dosage

There is no established oral supplemental dose for isolated geraniol, and nothing here is a recommendation. Food/flavoring use is bounded by the JECFA group ADI (0.5 mg/kg body weight/day); the one human trial used a low-absorbable geraniol supplement once daily for 4 weeks — a product-specific formulation, not a generic dose ^{11Reference 11Ricci C et al. · 2022RCTGeraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial — randomised controlled trialView study →}; and preclinical rodent efficacy used ~100–400 mg/kg orally, far above any dietary exposure ^{8Reference 8Babukumar S et al. · 2017AnimalGeraniol ameliorates hyperglycemia by attenuating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic ratsView study →}. Repellent formulations are typically ~5% topical or vapor ^{10Reference 10Müller GC et al. · 2009Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoesView study →}.

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

References

1. Mączka W, et al. (2020). One hundred faces of geraniol. Molecules. https://pubmed.ncbi.nlm.nih.gov/32708169/
2. Cho M, et al. (2016). The antitumour effects of geraniol: modulation of cancer hallmark pathways (review). International Journal of Oncology. https://pubmed.ncbi.nlm.nih.gov/26983575/
3. Duncan RE, et al. (2004). Geraniol and β-ionone inhibit proliferation, cell-cycle progression and CDK2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activity. Biochemical Pharmacology. https://pubmed.ncbi.nlm.nih.gov/15450939/
4. Pavan B, et al. (2018). Geraniol pharmacokinetics, bioavailability and its multiple effects on the liver antioxidant and xenobiotic-metabolising enzymes. Frontiers in Pharmacology. https://pubmed.ncbi.nlm.nih.gov/29422862/
5. Jäger T, Koch HM, Leibold E, et al. (2023). Human Metabolism and Urinary Elimination Kinetics of the Fragrance Geraniol after Oral Dosage — human volunteers. Chem Res Toxicol. https://pubmed.ncbi.nlm.nih.gov/37921539/
6. Medicherla K, Sahu BD, Kuncha M, et al. (2015). Oral administration of geraniol ameliorates acute experimental murine colitis by inhibiting pro-inflammatory cytokines and NF-κB signalling. Food & Function. https://pubmed.ncbi.nlm.nih.gov/26190278/
7. Soubh AA, Abdallah DM, El-Abhar HS, et al. (2015). Geraniol ameliorates TNBS-induced colitis: involvement of Wnt/β-catenin, p38 MAPK, NF-κB and PPARγ signalling pathways. Life Sciences. https://pubmed.ncbi.nlm.nih.gov/26165751/
8. Babukumar S, Vinothkumar V, Sankaranarayanan C, et al. (2017). Geraniol ameliorates hyperglycemia by attenuating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats. Pharmaceutical Biology. https://pubmed.ncbi.nlm.nih.gov/28330423/
9. Pereira Fde O, et al. (2015). Antifungal activity of geraniol and citronellol against Trichophyton rubrum involves inhibition of ergosterol biosynthesis. Pharmaceutical Biology. https://pubmed.ncbi.nlm.nih.gov/25414073/
10. Müller GC, et al. (2009). Efficacy of the botanical repellents geraniol, linalool and citronella against mosquitoes. Journal of Vector Ecology. https://pubmed.ncbi.nlm.nih.gov/20836800/
11. Ricci C, Rizzello F, Valerii MC, et al. (2022). Geraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial — randomised controlled trial. Nutrients. https://pubmed.ncbi.nlm.nih.gov/36235860/
12. 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/
13. 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/
14. Mahant S, Sahajpal NS, Nanda S (2021). Insights into the mechanism of Cymbopogan martinii essential oil in topical therapy of acne vulgaris — GC-MS composition and in vitro study. Future Microbiol. https://pubmed.ncbi.nlm.nih.gov/34615379/
15. Hernandez-Leon A, González-Trujano ME, Narváez-González F, et al. (2020). Role of β-Caryophyllene in the Antinociceptive and Anti-Inflammatory Effects of Tagetes lucida Cav. Essential Oil — GC-MS composition and mouse animal model. Molecules. https://pubmed.ncbi.nlm.nih.gov/32033302/
16. Ekpenyong CE, Akpan E, Nyoh A (2015). Ethnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts — review. Chin J Nat Med. https://pubmed.ncbi.nlm.nih.gov/25986281/
17. Magnard JL, Roccia A, Caissard JC, et al. (2015). PLANT VOLATILES. Biosynthesis of monoterpene scent compounds in roses — plant biochemistry, in vitro enzyme characterisation. Science. https://pubmed.ncbi.nlm.nih.gov/26138978/
18. Conart C, Saclier N, Foucher F, et al. (2022). Duplication and Specialization of NUDX1 in Rosaceae Led to Geraniol Production in Rose Petals — plant genomics study. Mol Biol Evol. https://pubmed.ncbi.nlm.nih.gov/35022771/
19. Simkin AJ, Miettinen K, Claudel P, et al. (2013). Characterization of the plastidial geraniol synthase from Madagascar periwinkle which initiates the monoterpenoid branch of the alkaloid pathway in internal phloem associated parenchyma — enzyme characterisation, in vitro. Phytochemistry. https://pubmed.ncbi.nlm.nih.gov/23102596/
20. Hagvall L, Bäcktorp C, Svensson S, et al. (2007). Fragrance compound geraniol forms contact allergens on air exposure. Identification and quantification of oxidation products and effect on skin sensitization — chemical analysis and mouse local lymph node assay, animal model. Chem Res Toxicol. https://pubmed.ncbi.nlm.nih.gov/17428070/
21. Behr A, Johnen L (2009). Myrcene as a natural base chemical in sustainable chemistry: a critical review — review. ChemSusChem. https://pubmed.ncbi.nlm.nih.gov/20013989/
22. Surendran S, Qassadi F, Surendran G, et al. (2021). Myrcene-What Are the Potential Health Benefits of This Flavouring and Aroma Agent? — review. Front Nutr. https://pubmed.ncbi.nlm.nih.gov/34350208/

View all 22 references▾