# Fennel essential oil > A licorice-scented herbal oil supporting digestive comfort as a dietary supplement, with caution needed for hormone-sensitive conditions. Canonical page: https://essential-oils.club/oils/single/fennel Type: Single oil ## At a glance - **Botanical name:** Foeniculum vulgare - **Plant part:** Seeds - **Extraction:** Steam-distilled - **Aroma:** Sweet, licorice-like - **Origin:** Mediterranean - **Blends with:** Orange, grapefruit, peppermint ## Composition (GC-MS research aggregate) Based on 59 GC-MS samples from 21 peer-reviewed papers (2020–2026); Strong evidence base. 81 compounds reported in total. Typical share of the oil (median, with interquartile range): | Compound | Class | Median % | IQR % | Max % | Papers | |---|---|---|---|---|---| | anethole | Phenylpropanoid / aromatic | 55.27 | 42.27–74.89 | 78.35 | 15 | | fenchone | Oxygenated monoterpene | 6.47 | 3.4–8.53 | 24.72 | 16 | | limonene | Monoterpene hydrocarbon | 5.29 | 2.69–15.25 | 26.8 | 19 | | estragole | Phenylpropanoid / aromatic | 4.36 | 2.87–7.28 | 26.81 | 16 | | α-pinene | Monoterpene hydrocarbon | 1.15 | 0.67–2.26 | 6.5 | 16 | | α-phellandrene | Monoterpene hydrocarbon | 1 | 0.14–4.5 | 12.05 | 11 | | γ-terpinene | Monoterpene hydrocarbon | 0.72 | 0.33–1.03 | 35.5 | 14 | | p-cymene | Monoterpene hydrocarbon | 0.8 | 0.31–2 | 6.8 | 9 | | myrcene | Monoterpene hydrocarbon | 0.5 | 0.21–1.1 | 5.1 | 13 | | 1,8-cineole | Oxygenated monoterpene | 0.33 | 0.2–0.5 | 7.15 | 10 | | β-pinene | Monoterpene hydrocarbon | 0.35 | 0.3–0.64 | 2.1 | 9 | | camphene | Monoterpene hydrocarbon | 0.22 | 0.1–0.24 | 0.82 | 9 | Chemotypes seen in the samples: anethole (64% of samples), e-anethole (7% of samples), estragole (5% of samples), trans-anethol (5% of samples). ## Key constituents - **trans-Anethole** (60-80%) — The dominant compound responsible for fennel's sweet, licorice-like character - **Fenchone** — A minor ketone adding a bitter-camphoraceous facet - **Estragole** — A minor aromatic ether also found in basil and tarragon ## How to use it - **In the diffuser:** 2–3 drops for a sweet, comforting, slightly spicy after-dinner atmosphere. - **Mind the hormones:** Fennel has mild estrogen-like activity — avoid concentrated use during pregnancy. ## Safety - Fennel contains compounds with mild estrogen-like activity — avoid regular or concentrated use during pregnancy, while breastfeeding, or with hormone-sensitive conditions. - Maximum dermal use: Dilute low in a carrier oil for skin. - High in trans-anethole (with some estragole): traditionally avoided during pregnancy, and best avoided by people with estrogen-sensitive conditions or epilepsy. - Use conservatively; not for young children. - Not phototoxic. Keep out of reach of children. ## What the research says - Fennel oil's trans-anethole has been studied for a range of activities and is noted for a mild estrogen-like reputation. Evidence is preliminary, and the anethole/estragole content is the reason for its cautious-use guidance rather than a health endorsement. — JEOB study (2011) (https://doi.org/10.1080/0972060x.2011.10643978) ## Evidence - Sweet fennel oil is dominated by trans-anethole — usually around 70% — which defines both its sweet, liquorice-like aroma and its cautious-use profile. — JEOB study (2011) (https://doi.org/10.1080/0972060x.2011.10643978) ## Frequently asked questions ### Why is fennel oil cautioned during pregnancy? Fennel is high in trans-anethole, which has a mild estrogen-like reputation, plus some estragole. For that reason it's traditionally avoided during pregnancy and by people with estrogen-sensitive conditions — check with a professional. ### Why does fennel smell like liquorice? Its dominant constituent, trans-anethole, is the same sweet, anise-like compound found in anise and star anise — which is why they all share that liquorice character. ### Is fennel oil phototoxic? No — fennel isn't phototoxic. The main precautions relate to its anethole/estragole content, not sun exposure. ## Sources (GC-MS studies) - Rasouli F, Nasiri Y, Hassanpouraghdam MB, Asadi M, Qaderi T, Trifa A, Strzemski M, Dresler S, Szczepanek M. Seaweed extract and arbuscular mycorrhiza co-application affect the growth responses and essential oil composition of Foeniculum vulgare L. _Scientific reports_, 2023. https://europepmc.org/article/PMC/PMC10366162 - Vučak A, Generalić Mekinić I, Brzović P, Skroza D, Frleta Matas R, Burčul F. Unlocking the Aromatic Profile of Wild-Grown Croatian Fennel: A Comparative Study of Essential Oils and Hydrolates. _Molecules (Basel, Switzerland)_, 2026. https://europepmc.org/article/PMC/PMC13258562 - Gad N, Fekry Ali ME, Elrahman EAA, Ismail HG, Yousef AF. Optimizing sweet fennel growth and quality: the impact of cobalt supplement on vegetative growth, yield, and chemical composition. _BMC plant biology_, 2025. https://europepmc.org/article/PMC/PMC12439422 - Baky MH, Elkenawy NM, El-Nashar HAS, Abib B, Farag MA. Comparison of autoclaving and γ-radiation impact on four spices aroma profiles and microbial load using HS-SPME GC-MS and chemometric tools. _Scientific reports_, 2024. https://europepmc.org/article/PMC/PMC10923872 - Afifi SM, El-Mahis A, Heiss AG, Farag MA. Gas Chromatography-Mass Spectrometry-Based Classification of 12 Fennel (Foeniculum vulgare Miller) Varieties Based on Their Aroma Profiles and Estragole Levels as Analyzed Using Chemometric Tools. _ACS omega_, 2021. https://europepmc.org/article/PMC/PMC7931402 - Božović M, Garzoli S, Vujović S, Sapienza F, Ragno R. Foeniculum vulgare Miller, a New Chemotype from Montenegro. _Plants (Basel, Switzerland)_, 2021. https://europepmc.org/article/PMC/PMC8747267 - Slišković L, Režić Mužinić N, Politeo O, Brzović P, Tomaš J, Generalić Mekinić I, Popović M. Biological Activities of Essential Oils and Hydrolates from Different Parts of Croatian Sea Fennel (<i>Crithmum maritimum</i> L.). _Biomolecules_, 2025. https://europepmc.org/article/PMC/PMC12108800 - Raza MH, Ayub MA, Zubair M, Hussain A, Saleem S, Azam MT, Hussain M, Memon AG, Abdelgawad MA, Ghoneim MM, El-Ghorab AH, Mostafa EM, Al Jbawi E. Comparative Study of Essential Oils Extracted From <i>Foeniculum vulgare</i> Miller Seeds Using Hydrodistillation, Steam Distillation, and Superheated Steam Distillation. _Food science & nutrition_, 2024. https://europepmc.org/article/PMC/PMC11667025 - EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), Bampidis V, Azimonti G, Bastos ML, Christensen H, Durjava M, Kouba M, López-Alonso M, López Puente S, Marcon F, Mayo B, Pechová A, Petkova M, Ramos F, Villa RE, Woutersen R, Brantom P, Chesson A, Schlatter J, Westendorf J, Dirven Y, Manini P, Pizzo F, Dusemund B. Safety and efficacy of feed additives consisting of essential oils from the fruit and stems of Foeniculum vulgare Mill. ssp. vulgare: Bitter fennel oil for use in all animal species and sweet fennel oil for use in dogs and cats (FEFANA asbl). _EFSA journal. European Food Safety Authority_, 2023. https://europepmc.org/article/PMC/PMC10613937 - Félix BP, Rodrigues A, Sousa MJ, Pereira OR. Effect of Aromatherapy Massage With <i>Foeniculum vulgare</i> Mill. Seed Essential Oil Compared to Massage on Anxiety, Well-Being, and Sleep Quality: An Exploratory Randomized Study. _Health science reports_, 2026. https://europepmc.org/article/PMC/PMC13172767 - Santoro V, Rosa E, Donadio G, Polito F, De Feo V, De Tommasi N. Foeniculum vulgare Miller bracts, revalorization of a local food waste. _Scientific reports_, 2024. https://europepmc.org/article/PMC/PMC11682140 - Cebollada P, Spinozzi E, Ferrati M, Moliner C, Petrelli R, Maggi F, Gomez-Rincón C, López V. <i>Anisakis simplex</i> larvae viability and potential pathogenicity in vitro is controlled by the essential oil from sea fennel (<i>Crithmum maritinum</i> L., Apiaceae). _Food and waterborne parasitology_, 2026. https://europepmc.org/article/PMC/PMC13054408 - Iommelli P, Musco N, Lombardi P, Spina AA, Morittu VM, Sarubbi F, Tufarelli V, Ceci E, Infascelli F, Tudisco R. Dietary fennel (Foeniculum vulgare Mill) seeds supplementation affects yield, fatty acid composition and flavour profile of milk and cheese in grazing goats. _Tropical animal health and production_, 2025. https://europepmc.org/article/PMC/PMC12058878 - Soleymanzadeh A, Valizadegan O, Saber M, Hamishehkar H. Toxicity of Foeniculum vulgare essential oil, its main component and nanoformulation against Phthorimaea absoluta and the generalist predator Macrolophus pygmaeus. _Scientific reports_, 2025. https://europepmc.org/article/PMC/PMC12078669 - Elkiran O, Telhuner O. Chemical Profiles and Antimicrobial Activities of Essential Oil From Different Plant Parts of Fennel (<i>Foeniculum vulgare</i> Mill.). _Food science & nutrition_, 2025. https://europepmc.org/article/PMC/PMC12086306 - Moumen BE, Bouzoubaa A, Drioiche A, Eddahmouny M, Al Kamaly O, Shahat AA, Touijer H, Hadi N, Kharchouf S, Cherrat A, Fadili K, El Ouadni H, Bari A, Zair T. Unveiling the Chemical Composition, Antioxidant, and Antimicrobial Potentials of <i>Foeniculum vulgare</i> Mill: A Combined In Vitro and In Silico Approach. _International journal of molecular sciences_, 2025. https://europepmc.org/article/PMC/PMC12111592 - Türkmen M, Gezici S, Karahan F. Phytochemical composition and biological activities of selected essential oils and their discrimination through principal component analysis. _Scientific reports_, 2025. https://europepmc.org/article/PMC/PMC12824334 - Metin S, Didinen H, Yigit NO, Eralp H, Ozmen O, Avsever ML. Efficacy of fennel (Foeniculum vulgare) and anise (Pimpinella anisum) essential oils as anaesthesics in common carp (Cyprinus carpio L. 1758). _Fish physiology and biochemistry_, 2024. https://europepmc.org/article/PMC/PMC11213784 - Ștefănescu R, Ősz BE, Pintea A, Laczkó-Zöld E, Tero-Vescan A, Vari CE, Fulop E, Blaș I, Vancea S. Fennel Essential Oil as a Complementary Therapy in the Management of Diabetes. _Pharmaceutics_, 2023. https://europepmc.org/article/PMC/PMC10747567 - De-Montijo-Prieto S, Razola-Díaz MDC, Gómez-Caravaca AM, Guerra-Hernandez EJ, Jiménez-Valera M, Garcia-Villanova B, Ruiz-Bravo A, Verardo V. Essential Oils from Fruit and Vegetables, Aromatic Herbs, and Spices: Composition, Antioxidant, and Antimicrobial Activities. _Biology_, 2021. https://europepmc.org/article/PMC/PMC8615279 - …and 1 more on the canonical page. _Educational reference only — not medical advice. Essential oils are not intended to diagnose, treat, cure or prevent any disease._