Fennel (Foeniculum vulgare)
A licorice-scented herbal oil supporting digestive comfort as a dietary supplement, with caution needed for hormone-sensitive conditions.
How to use it
2–3 drops for a sweet, comforting, slightly spicy after-dinner atmosphere.
Fennel has mild estrogen-like activity — avoid concentrated use during pregnancy.
Safety in detail
- Max dermal use
- Dilute low in a carrier oil for skin
- Phototoxic
- No
- 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.
Sources: JEOB study (2011)
Composition & chemistry
Aggregated from 59 GC-MS samples across 21 peer-reviewed open-access studies (2020–2026). Figures are the distribution across those samples — median with interquartile range — not a single reading.
- Phenylpropanoid / aromatic 69.2%
- Monoterpene hydrocarbon 16.9%
- Oxygenated monoterpene 12.4%
- Unclassified 1.6%
| Constituent | Median | Typical range | Max | Detected in |
|---|---|---|---|---|
| anethole ↗ C10H12O | 55.3% | 42.3–74.9% | 78.3% | |
Loading evidence… | ||||
| fenchone ↗ C10H16O | 6.5% | 3.4–8.5% | 24.7% | |
Loading evidence… | ||||
| limonene ↗ C10H16 | 5.3% | 2.7–15.3% | 26.8% | |
Loading evidence… | ||||
| estragole ↗ C10H12O | 4.4% | 2.9–7.3% | 26.8% | |
Loading evidence… | ||||
| α-pinene ↗ C10H16 | 1.1% | 0.7–2.3% | 6.5% | |
Loading evidence… | ||||
| α-phellandrene ↗ C10H16 | 1.0% | 0.1–4.5% | 12.1% | |
Loading evidence… | ||||
| p-cymene ↗ C10H14 | 0.8% | 0.3–2.0% | 6.8% | |
Loading evidence… | ||||
| γ-terpinene ↗ C10H16 | 0.7% | 0.3–1.0% | 35.5% | |
Loading evidence… | ||||
| myrcene ↗ C10H16 | 0.5% | 0.2–1.1% | 5.1% | |
Loading evidence… | ||||
| β-pinene ↗ C10H16 | 0.3% | 0.3–0.6% | 2.1% | |
Loading evidence… | ||||
| 1,8-cineole ↗ C10H18O | 0.3% | 0.2–0.5% | 7.2% | |
Loading evidence… | ||||
| camphene ↗ C10H16 | 0.2% | 0.1–0.2% | 0.8% | |
Loading evidence… | ||||
+ 69 more compounds reported across the dataset.
21 peer-reviewed sources behind these figures
- Rasouli F, Nasiri Y, Hassanpouraghdam MB, Asadi M, Qaderi T, Trifa A, Strzemski M, Dresler S, Szczepanek M. (2023). Seaweed extract and arbuscular mycorrhiza co-application affect the growth responses and essential oil composition of Foeniculum vulgare L. Scientific reports.
- Vučak A, Generalić Mekinić I, Brzović P, Skroza D, Frleta Matas R, Burčul F. (2026). Unlocking the Aromatic Profile of Wild-Grown Croatian Fennel: A Comparative Study of Essential Oils and Hydrolates. Molecules (Basel, Switzerland).
- Gad N, Fekry Ali ME, Elrahman EAA, Ismail HG, Yousef AF. (2025). Optimizing sweet fennel growth and quality: the impact of cobalt supplement on vegetative growth, yield, and chemical composition. BMC plant biology.
- Baky MH, Elkenawy NM, El-Nashar HAS, Abib B, Farag MA. (2024). 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.
- Afifi SM, El-Mahis A, Heiss AG, Farag MA. (2021). 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.
- Božović M, Garzoli S, Vujović S, Sapienza F, Ragno R. (2021). Foeniculum vulgare Miller, a New Chemotype from Montenegro. Plants (Basel, Switzerland).
- Slišković L, Režić Mužinić N, Politeo O, Brzović P, Tomaš J, Generalić Mekinić I, Popović M. (2025). Biological Activities of Essential Oils and Hydrolates from Different Parts of Croatian Sea Fennel (<i>Crithmum maritimum</i> L.). Biomolecules.
- 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. (2024). Comparative Study of Essential Oils Extracted From <i>Foeniculum vulgare</i> Miller Seeds Using Hydrodistillation, Steam Distillation, and Superheated Steam Distillation. Food science & nutrition.
- 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. (2023). 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.
- Félix BP, Rodrigues A, Sousa MJ, Pereira OR. (2026). 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.
- Santoro V, Rosa E, Donadio G, Polito F, De Feo V, De Tommasi N. (2024). Foeniculum vulgare Miller bracts, revalorization of a local food waste. Scientific reports.
- Cebollada P, Spinozzi E, Ferrati M, Moliner C, Petrelli R, Maggi F, Gomez-Rincón C, López V. (2026). <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.
- Iommelli P, Musco N, Lombardi P, Spina AA, Morittu VM, Sarubbi F, Tufarelli V, Ceci E, Infascelli F, Tudisco R. (2025). 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.
- Soleymanzadeh A, Valizadegan O, Saber M, Hamishehkar H. (2025). Toxicity of Foeniculum vulgare essential oil, its main component and nanoformulation against Phthorimaea absoluta and the generalist predator Macrolophus pygmaeus. Scientific reports.
- Elkiran O, Telhuner O. (2025). Chemical Profiles and Antimicrobial Activities of Essential Oil From Different Plant Parts of Fennel (<i>Foeniculum vulgare</i> Mill.). Food science & nutrition.
- 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. (2025). 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.
- Türkmen M, Gezici S, Karahan F. (2025). Phytochemical composition and biological activities of selected essential oils and their discrimination through principal component analysis. Scientific reports.
- Metin S, Didinen H, Yigit NO, Eralp H, Ozmen O, Avsever ML. (2024). Efficacy of fennel (Foeniculum vulgare) and anise (Pimpinella anisum) essential oils as anaesthesics in common carp (Cyprinus carpio L. 1758). Fish physiology and biochemistry.
- Ștefănescu R, Ősz BE, Pintea A, Laczkó-Zöld E, Tero-Vescan A, Vari CE, Fulop E, Blaș I, Vancea S. (2023). Fennel Essential Oil as a Complementary Therapy in the Management of Diabetes. Pharmaceutics.
- De-Montijo-Prieto S, Razola-Díaz MDC, Gómez-Caravaca AM, Guerra-Hernandez EJ, Jiménez-Valera M, Garcia-Villanova B, Ruiz-Bravo A, Verardo V. (2021). Essential Oils from Fruit and Vegetables, Aromatic Herbs, and Spices: Composition, Antioxidant, and Antimicrobial Activities. Biology.
- Oro V, Krnjajic S, Tabakovic M, Stanojevic JS, Ilic-Stojanovic S. (2020). Nematicidal Activity of Essential Oils on a Psychrophilic Panagrolaimus sp. (Nematoda: Panagrolaimidae). Plants (Basel, Switzerland).
Every figure above traces to a named table in one of these open-access papers. How this was built →
- trans-Anethole — the dominant phenylpropene behind fennel's liquorice-like aroma and its mild estrogen-like reputation in studies JEOB study (2011)
Trans-anethole gives fennel the same sweet, licorice-like smell as anise and star anise.
What the research says
An honest read of the published research — what has actually been studied, at what stage. Not medical advice or a promise of results.
-
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)
Evidence & sources
Peer-reviewed research on Fennel's chemistry and safety. These describe composition and documented effects — not health or treatment claims.
-
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)
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. JEOB study (2011)
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. JEOB study (2011)
Is fennel oil phototoxic?
No — fennel isn't phototoxic. The main precautions relate to its anethole/estragole content, not sun exposure.
Gallery
Fennel (Foeniculum vulgare) is a Mediterranean herb grown for its edible bulb, feathery leaves, and aromatic seeds, the last of which are steam-distilled to produce this oil. The result carries the same anise-like, licorice-sweet aroma as the whole spice, concentrated into a form suited to diffusing, diluted topical use, or — via the separate Vitality bottle — dietary use.
Aroma & Composition
Trans-anethole makes up 60–80% of the oil and is responsible for its dominant sweet, licorice-like character, the same compound that gives anise and star anise their similar smell. Smaller amounts of fenchone add a slightly bitter, camphoraceous facet, while estragole — also found in basil and tarragon — contributes a faint herbal complexity underneath the sweetness.
Traditional & Everyday Uses
In the diffuser: 2–3 drops gives a sweet, comforting, slightly spicy scent that works well in the evening or as part of a calming after-dinner atmosphere, echoing fennel’s long culinary association with meals.
As a supplement: the separate Fennel Vitality bottle is labeled for dietary use and is traditionally used the way ground fennel seed is used in cooking or herbal tea — a small addition to a normal routine rather than a concentrated remedy.
Pairs Well With
Citrus oils like orange or grapefruit complement fennel’s sweetness; peppermint adds a cooling contrast for an after-meal diffuser blend.
Safety Note
Fennel contains compounds with mild estrogen-like activity, a property well documented in the plant’s traditional use. It’s generally advised to avoid regular or concentrated use during pregnancy, while breastfeeding, or with hormone-sensitive conditions — check with a healthcare provider if any of these apply to you before making fennel oil a regular part of your routine, whether aromatic, topical, or dietary.
Found in these blends
Fennel is one of the oils inside 5 Young Living blends.