Fennel
In short
Summary of findings for quick reference
Fennel has a written record since antiquity. Dioscorides and Pliny described different plant parts and uses. In the early Middle Ages, the Capitulare de villis listed fennel among the plants wanted in royal estate gardens; Walahfrid Strabo’s Hortulus also described medicinal uses. Later herbals and modern herbal medicine continued the record. These sources establish a long history, but not uninterrupted or independent use in every tradition listed here.
The EMA recognises the traditional use of sweet and bitter fennel fruit for mild spasmodic gastrointestinal complaints including bloating and flatulence. Laboratory findings support its plausibility, but clinical evidence remains limited. Classification as a traditional herbal medicine should therefore not be read as evidence of well-established clinical efficacy.
Infant-colic studies have tested a fennel-oil emulsion and an extract of chamomile, fennel and lemon balm, among other preparations. Their results cannot be transferred to home-brewed fennel tea. Estragole is also relevant to tea. The EMA does not recommend medicinal use below age four; older children have additional limits for estragole content and duration of use.
Clinical evidence ↔ Historical significanceWe display two separate evidence categories: clinical evidence from modern trials and historical significance from documented healing tradition. Both are valuable, but they answer different questions.Read more
In every encyclopedia entry we evaluate two distinct categories of evidence. Clinical evidence as used in trials meets a narrower but scientifically essential bar. At the same time, the hundreds of thousands of plant species worldwide have only partially been captured and tested in modern studies.
Alongside the trial picture our researchers compile a comprehensive overview of where and since when a plant has been used across different traditions of natural medicine. When a plant has been used as a medicinal plant in many cultures across many generations, that historical significance deserves to be visible too.
Our position: a truly informative overview emerges only when both categories sit side by side. We communicate transparently what counts as what.
Overview
Fennel (Foeniculum vulgare) is an aromatic, usually perennial herb in the Apiaceae family, with finely divided, almost hair-like leaves and a sweet anise scent. The ripe fruits, commonly called fennel seeds, are the main part used. The European Medicines Agency (EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC)) lists sweet and bitter fennel fruit as traditional herbal medicines for mild spasmodic gastrointestinal complaints including bloating and flatulence, and as an expectorant for cough associated with colds. This classification rests on long-standing use and does not establish clinical efficacy.
Fennel is familiar in Austrian and German-speaking garden traditions and in fennel-anise-caraway tea. Its essential oil contains anethole, fenchone and estragole, among other compounds. Tea can also contain estragole, with amounts depending on the material and preparation. Medicinal use therefore has age and duration limits. Fennel tea should not be given to infants as a home remedy.
History
Fennel is documented as a medicinal and food plant since Greek and Roman antiquity. Under marathron in De materia medica, Dioscorides describes uses of the herb, fruits, root and juice. Pliny mentions fennel as a culinary ingredient and lists numerous contemporary medicinal uses. These texts establish the plant’s historical significance, not the efficacy of the remedies.
In medieval Europe, fennel was a garden and medicinal plant. Walahfrid Strabo devotes a section to it in the ninth-century Hortulus, mentioning abdominal complaints among other uses. The Capitulare de villis from around 800 lists fennel among the plants wanted for royal estates; the list itself contains no medicinal instructions. Later herbals continue the record. Fennel-anise-caraway is now a familiar herbal tea, and the EMA describes the medicinal use of fennel fruit as traditional use.
Mechanism
trans-Anethole, a phenylpropene, contributes to fennel’s sweet anise scent and is a major component of sweet fennel essential oil (var. dulce). Bitter fennel (var. vulgare) contains more fenchone, a bitter-tasting monoterpene ketone. Fennel extracts and essential oil have been investigated in experimental models, including for smooth-muscle relaxation. These findings offer a possible explanation for traditional use for cramps and flatulence, but do not establish a corresponding benefit of a cup of tea in humans.
Estragole is another constituent of fennel oil and can also pass into tea. Genotoxic and carcinogenic findings in experimental studies mean that exposure from herbal medicines should be kept as low as possible. This supports neither a blanket reassurance about tea nor a quantified cancer risk from a single cup. Experimental indications of hormonal activity of individual constituents likewise do not establish a hormonal benefit of fennel tea in humans.
Modern research on fennel complements a long tradition of use. The EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC) classifies both sweet and bitter fennel fruit as traditional herbal medicines, including for mild spasmodic gastrointestinal complaints with bloating and flatulence and for cough associated with colds. These monographs do not grant well-established-use status. Experimental findings on smooth-muscle relaxation support plausibility but do not replace sufficiently robust clinical trials.
A randomised trial by Alexandrovich and colleagues (2003), enrolling 125 infants, reported less colic with a fennel-oil emulsion than with placebo. Savino and colleagues (2005) enrolled 93 infants in a trial of a combined chamomile, fennel and lemon-balm extract and reported reduced crying time. These were different preparations, and the second trial does not establish a benefit of fennel alone. Neither trial establishes a recommendation for home-brewed fennel tea or long-term safety in infants. The current EMA age restriction still applies.
Usage
Forms and preparation
Follow the preparation instructions on the package of a finished medicinal tea. Do not additionally crush the fruit on your own initiative, as this can release more estragole into the tea. For the adult dose described in the dosage section, the EMA monographs specify 1.5 g fruit in 250 ml boiling water, steeped for 15 minutes. Steep covered, then strain. Fennel-anise-caraway tea combines the fruits of these three plants. The ratio depends on the product or recipe; for medicinal tea, follow its preparation, dose and age limits. The blend is not a general recommendation for infants or children. Concentrated fennel oil must not be dosed using tea instructions.
Dosage
For adults and adolescents aged twelve and over, the EMA monographs specify 1.5 g fennel fruit per 250 ml water three times daily for mild digestive complaints, totalling 4.5 g per day. Medicinal use should last no more than two weeks. It is not recommended below age four. For children aged four to eleven, only suitable products for short-term use should be considered; a “weak cup” cannot reliably meet the estragole requirements. Seek advice from a pharmacist or paediatrician. Follow the package leaflet for medicinal products; tea doses do not automatically apply to extracts, capsules or syrups. For children aged four to eleven, the EMA monographs limit use for digestive complaints and cough associated with colds to less than one week and make it conditional on estragole exposure. Seek medical advice if symptoms persist or worsen. Fennel essential oil is not a substitute for tea and should not be used internally without professional guidance.
Safety
Look-alikes
Similar plants and look-alikes
Poison hemlock (Conium maculatum)
Poison hemlock is a deadly toxic member of the Apiaceae. It can resemble fennel in habit, but has white rather than yellow flowers and usually purple-blotched stems. Its often unpleasant smell is not a reliable identification test. Leave unidentified plants in the wild or at garden edges alone.
Anise (Pimpinella anisum)
Anise (Pimpinella anisum) is a related Apiaceae plant with a similar scent and traditional use. It is usually much shorter and has white flowers; its lower leaves are broader than fennel’s finely divided leaves. The two species are combined in fennel-anise-caraway tea, but are distinct plants.
Read the entry: AniseFAQs
What should parents know before giving fennel tea to babies?
The EMA does not recommend fennel herbal medicines for children under four because adequate data are lacking. This includes fennel tea. A home-prepared “weak cup” is not a validated infant dose and does not reliably control estragole exposure. Seek paediatric advice for persistent crying or digestive symptoms in your baby instead of using fennel tea or fennel oil for self-treatment.
What is Fenchel-Anis-Kuemmel?
Fennel-anise-caraway is a familiar herbal tea blend made from the fruits of fennel, anise and caraway. All three plants have traditional uses for mild digestive complaints. Recipes and proportions vary; equal parts are one option. This tradition does not establish general suitability as a children’s tea. For medicinal teas, follow the leaflet and age restrictions.
Should I crush fennel seeds before brewing?
Follow the preparation instructions for packaged medicinal tea. Crushing the fruits, commonly called seeds, can also release more estragole into the tea. The EMA therefore removed comminuted fruit from its 2024 monographs. Do not additionally crush the fruit on your own initiative.
Is fennel essential oil the same as fennel tea?
No. Fennel tea is an aqueous infusion of the fruits, whereas fennel essential oil is a concentrated distillate. Both can contain estragole, but their composition and dosing differ substantially. A tea’s safety assessment therefore cannot be transferred to oil. Do not use concentrated fennel oil for internal self-treatment, especially in children. Guidance on pregnancy, breastfeeding and age restrictions also applies to medicinal tea.
5 sources.
- European Medicines Agency, HMPC. European Union herbal monograph on sweet fennel fruit, Revision 1. 2024. Source
- European Medicines Agency, HMPC. European Union herbal monograph on bitter fennel fruit, Revision 1. 2024. Source
- European Medicines Agency, HMPC. Assessment report on bitter and sweet fennel fruit, Revision 1. 2024. Source
- Irina Alexandrovich; Olga Rakovitskaya; Elena Kolmo; Tatyana Sidorova; Sergei Shushunov. The effect of fennel (Foeniculum Vulgare) seed oil emulsion in infantile colic: a randomized, placebo-controlled study. 2003. PMID:12868253
- Francesco Savino; Francesco Cresi; Emanuele Castagno; Leandra Silvestro; Roberto Oggero. A randomized double-blind placebo-controlled trial of a standardized extract of Matricariae recutita, Foeniculum vulgare and Melissa officinalis (ColiMil) in the treatment of breastfed colicky infants. 2005. doi:10.1002/ptr.1668
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