Omnia Sana · Plant Monograph
Fennel
Foeniculum vulgare
This monograph compiles 4 documented constituents, 3 pharmacological actions, 8 traditional / indicated uses, supported by 12 cited sources, drawn directly from the Omnia Sana plant database.
Key Constituents
The aromatic volatile oil of the seed; trans-anethole is the principal component and is associated with the antispasmodic, carminative and estrogen-like activity.
Antioxidant polyphenolic constituents.
Antioxidant and anti-inflammatory constituents.
Major constituents of the fruit/seed oil.
Pharmacological Actions
Traditional & Indicated Uses
inferred from expectorant action
more plants for bronchitis →detailed sources →inferred from expectorant action
more plants for cough →detailed sources →inferred from antimicrobial action
more plants for infection (general) →detailed sources →Relieves primary dysmenorrhoea (menstrual) pain - meta-analyses of RCTs find fennel reduces pain intensity versus placebo, comparable to mefenamic acid
more plants for menstrual cramps →detailed sources →inferred from antispasmodic action
more plants for muscle spasm →detailed sources →Relieves primary dysmenorrhoea (menstrual) pain - meta-analyses of RCTs find fennel reduces pain intensity versus placebo, comparable to mefenamic acid
more plants for pain (general) →detailed sources →inferred from expectorant action
more plants for respiratory support →detailed sources →inferred from antimicrobial action
more plants for wounds →detailed sources →Safety, Cautions & Contraindications
When taken by mouth: Fennel is commonly consumed in foods. It is possibly safe when used as medicine at appropriate doses for a short period of time. There isn't enough reliable information to know whether fennel is safe when used long-term. Although rare, side effects might include stomach upset and seizures.
When applied to the skin: Fennel is possibly safe. Fennel can make skin extra sensitive to the sun and make it easier to get a sunburn. Wear sunblock if you are light-skinned. Special Precautions and Warnings When taken by mouth: Fennel is commonly consumed in foods. It is possibly safe when used as medicine at appropriate doses for a short period of time. There isn't enough reliable information to know whether fennel is safe when used long-term. Although rare, side effects might include stomach upset and seizures.
When applied to the skin: Fennel is possibly safe. Fennel can make skin extra sensitive to the sun and make it easier to get a sunburn. Wear sunblock if you are light-skinned.
Pregnancy: Fennel is possibly unsafe to use when pregnant. Regularly using fennel has been linked to preterm birth.
Breast-feeding: Fennel is possibly unsafe. There are some reports of breast-feeding infants with damage to their nervous systems after they were exposed to herbal tea containing fennel through breastmilk.
Children: Fennel is possibly safe when used at appropriate doses for up to one week in young infants with colic.
Allergy to celery, carrot or mugwort: Fennel might cause an allergic reaction in people who are sensitive to these plants.
Bleeding disorders: Fennel might slow blood clotting. Taking fennel might increase the risk of bleeding or bruising in people with bleeding disorders.
Hormone-sensitive condition such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Fennel might act like estrogen. If you have any condition that might be made worse by estrogen, do not use fennel. (WebMD, n.d.b)
Duke (2002) rates fennel as ++ and notes antispasmodic, carminative, and digestive activities at experimental levels (score 1). Its estrogenic activity is well-documented, and it is traditionally used as a lactagogue. Commission E approves fennel for dyspeptic complaints and upper respiratory tract catarrh. Dose: 1.5–7.5 g seed or equivalent daily. Duke cautions that fennel essential oil in large amounts may be neurotoxic (estrole content), and prolonged use of concentrated extracts should be avoided during pregnancy (Duke, 2002).
References
REF-1641, REF-1642, REF-0537, REF-1643, REF-1644, REF-0605, REF-1645, REF-1646, REF-1656, REF-1657References & Sources
- Rafieian, F., Amani, R., Rezaei, A. and others (2023) 'Exploring fennel (Foeniculum vulgare): Composition, functional properties, potential health benefits, and safety', Critical Reviews in Food Science and Nutrition, 64(19), pp. 6924-6941. doi:10.1080/10408398.2023.2176817 Meta-analysis / review
https://doi.org/10.1080/10408398.2023.2176817 - Khorshidi, M. and others (2021) 'Fennel (Foeniculum vulgare Miller) for the management of menopausal women's health: A systematic review and meta-analysis', Complementary Therapies in Clinical Practice, 43, pp. 101360. doi:10.1016/j.ctcp.2021.101360 Meta-analysis / review
https://doi.org/10.1016/j.ctcp.2021.101360 - Badgujar, S.B. and Patel, V.V. and Bandivdekar, A.H (2014) 'Foeniculum vulgare Mill: a review of its botany, phytochemistry, pharmacology, contemporary application, and toxicology', BioMed Research International. doi:10.1155/2014/842674 Traditional / reference
https://doi.org/10.1155/2014/842674 - Rasul, A. and others (2019) 'Foeniculum vulgare (Fennel) promotes functional recovery and ameliorates oxidative stress following a lesion to the sciatic nerve in mouse model', Journal of Food Biochemistry, 43(11), pp. e12983. doi:10.1111/jfbc.12983 Preclinical
https://doi.org/10.1111/jfbc.12983 - Rasheed, N. and others (2019) 'The Fennel, Foeniculum vulgare incorporated diet shows anxiolytic potential: A pre-clinical study', Pakistan Journal of Pharmaceutical Sciences, 32(4), pp. 1791-1797. Preclinical
Find this source - Xu, Y., Yang, Q. and Wang, X (2020) 'Efficacy of herbal medicine (cinnamon/fennel/ginger) for primary dysmenorrhea: a systematic review and meta-analysis of randomized controlled trials', Journal of International Medical Research, 48(6). doi:10.1177/0300060520936179 Meta-analysis / review
https://doi.org/10.1177/0300060520936179 - Bae, J. and others (2022) 'Olfactory Stimulation by Fennel (Foeniculum vulgare Mill.) Essential Oil Improves Lipid Metabolism and Metabolic Disorders in High Fat-Induced Obese Rats', Nutrients, 14(4), pp. 741. doi:10.3390/nu14040741 Preclinical
https://doi.org/10.3390/nu14040741 - Crescente, G. and others (2017) 'Fennel (Foeniculum vulgare Mill. subsp. piperitum) florets, a traditional culinary spice in Italy: evaluation of phenolics and volatiles in local populations, and comparison with the composition of other plant parts', Journal of the Science of Food and Agriculture, 98(5), pp. 1755-1765. doi:10.1002/jsfa.8426 Preclinical
https://doi.org/10.1002/jsfa.8426 - Yakut, H.I., Koyuncu, E., Cakir, U., Tayman, C. and others (2020) 'Preventative and therapeutic effects of fennel (Foeniculum vulgare) seed extracts against necrotizing enterocolitis', Journal of Food Biochemistry, 44(8), pp. e13284. doi:10.1111/jfbc.13284 Preclinical
https://doi.org/10.1111/jfbc.13284 - Kamali, F., Mojani-Qomi, M.S., Arbabi Bidgoli, S., Lavasani, Z. and Adineh, M (2025) 'Fennel (Foeniculum vulgare) oral capsules improve endometrial thickness in infertile women following clomiphene citrate treatment', European Journal of Obstetrics, Gynecology, and Reproductive Biology, 313, pp. 114638. doi:10.1016/j.ejogrb.2025.114638 Randomized trial
https://doi.org/10.1016/j.ejogrb.2025.114638 - https://www.webmd.com/vitamins/ai/ingredientmono-311/fennel. Available at: https://www.webmd.com/vitamins/ai/ingredientmono-311/fennel Traditional / reference
https://www.webmd.com/vitamins/ai/ingredientmono-311/fennel - Shahrahmani, H., Ghazanfarpour, M., Shahrahmani, N., Abdi, F., Sewell, R.D.E. and Rafieian-Kopaei, M (2021) 'Effect of fennel on primary dysmenorrhea: a systematic review and meta-analysis', Journal of Complementary & Integrative Medicine, 18(2), pp. 261--269. doi:10.1515/jcim-2019-0212 Meta-analysis / review
https://doi.org/10.1515/jcim-2019-0212
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