TempoLife › Features › Herb and spice reference: evidence, dose and interactions › fennel
Fennel
Fennel — what the European monograph actually supports, what it is not for, the form and how long it is meant to be used, side effects, and the absence of established medicine interactions documented for it.
This is a reference page, not a diagnosis and not a prescription. Herbal products are real pharmacology: they have effects, side effects and interactions with medicines. Tell your doctor and your pharmacist everything you take, including teas and supplements, and never stop or change a prescribed medicine because of anything you read here.
What it is
Foeniculum vulgare Mill. — fruit (Foeniculi amari fructus, Foeniculi dulcis fructus)
Local names across the region this site serves: apteegitill (ET) · fenkoli (FI) · фенхель (RU).
Grouped here under Digestion, bloating and the bowel. Regulatory position: EU herbal monograph — traditional use.
What the evidence supports
The registered indication: Mild spasmodic gastrointestinal complaints including bloating and flatulence; and as an expectorant in cough associated with a cold.
Fennel tea is the classic Baltic and Nordic answer to a windy baby, and that is exactly the use European regulators have looked at hardest. Fennel fruit contains estragole, a constituent it shares with anise and basil, which is genotoxic and carcinogenic in animal experiments. The herbal committee at the European Medicines Agency has published a position on estragole exposure from herbal medicinal products, and monograph texts restrict fennel-fruit preparations in young children as a result. That is not a claim that a cup of fennel tea harmed anyone; it is a precautionary limit on repeated exposure in the group with the lowest body weight and the longest life ahead. For a colicky baby, the honest advice is to ask the health nurse or pharmacist rather than to brew it on tradition alone.
C — Traditional use only Plausible from thirty or more years of use, which is what a traditional-use registration means. No clinical evidence was required and none has settled it.
What it is not for
Persistent infant crying with poor feeding, vomiting, fever or poor weight gain, which needs assessment. In adults, bloating with weight loss or a change in bowel habit also needs assessment.
Form, strength and how long
Crushed fruit as an infusion, fennel honey and syrups, and essential oil. Bitter and sweet fennel are distinguished in the monographs and differ in composition.
Duration. Short-term symptomatic use in adults; restricted use in children.
No gram figure appears on this page on purpose. The plant part, the extraction solvent and the drug-to-extract ratio together define a preparation, and a number taken from one does not describe another. The reasoning is set out on the hub; the amount that applies to you is the one printed on the pack you are holding, and a pharmacist will read it with you.
Side effects
Allergic reactions occur, including cross-reaction in people allergic to celery, carrot and mugwort (the Apiaceae group). Skin and airway allergy to fennel is documented.
Who should avoid it
Restricted in young children because of estragole. Not recommended in pregnancy or breastfeeding for medicinal preparations, despite widespread traditional use as a milk-promoting tea.
Interactions with medicines
No clinically important medicine interactions are established for this herb at culinary or tea amounts. That is not a guarantee — it means nothing has been characterised well enough to state. Concentrated extracts are a different exposure from a cup of tea, and the standing rule still applies: tell your pharmacist what you take.
The reverse view — start from the medicine rather than the plant — is in the medicine, food and alcohol interactions reference, and summarised for every herb on this site.
As a food
This one is also in the kitchen, so the nutrition figures are worth having next to the pharmacology: see the food data page for calories and nutrients per 100 g and per portion. Culinary amounts and medicinal preparations are different exposures, and the difference is usually the whole safety story.
Sources: European Medicines Agency — Committee on Herbal Medicinal Products (HMPC), European Union herbal monographs · checked 2026-09-06
Frequently asked questions
What is fennel used for?
Mild spasmodic gastrointestinal complaints including bloating and flatulence; and as an expectorant in cough associated with a cold. Fennel tea is the classic Baltic and Nordic answer to a windy baby, and that is exactly the use European regulators have looked at hardest. Fennel fruit contains estragole, a constituent it shares with anise and basil, which is genotoxic and carcinogenic in animal experiments. The herbal committee at the European Medicines Agency has published a position on estragole exposure from herbal medicinal products, and monograph texts restrict fennel-fruit preparations in young children as a result. That is not a claim that a cup of fennel tea harmed anyone; it is a precautionary limit on repeated exposure in the group with the lowest body weight and the longest life ahead. For a colicky baby, the honest advice is to ask the health nurse or pharmacist rather than to brew it on tradition alone.
Does fennel work?
Graded C here: Plausible from thirty or more years of use, which is what a traditional-use registration means. No clinical evidence was required and none has settled it. Persistent infant crying with poor feeding, vomiting, fever or poor weight gain, which needs assessment. In adults, bloating with weight loss or a change in bowel habit also needs assessment.
How much fennel should I take?
This reference does not print gram figures, because they do not transfer between preparations of different extract strength. What can be said honestly is the form and the duration: Crushed fruit as an infusion, fennel honey and syrups, and essential oil. Bitter and sweet fennel are distinguished in the monographs and differ in composition. Short-term symptomatic use in adults; restricted use in children.
What are the side effects of fennel?
Allergic reactions occur, including cross-reaction in people allergic to celery, carrot and mugwort (the Apiaceae group). Skin and airway allergy to fennel is documented.
Does fennel interact with medicines?
No clinically important medicine interactions are established for it, which is not the same as none existing. Tell your pharmacist what you take.
Others in digestion, bloating and the bowel
Peppermint
Symptomatic relief of minor spasms of the gastrointestinal tract, flatulence and abdominal pain, especially in irritable bowel syndrome, for gastro-resistant oil capsules; the leaf is registered for mild digestive complaints.
Caraway
Mild spasmodic gastrointestinal complaints including bloating and flatulence.
Ginger
Prevention of nausea and vomiting in motion sickness, and mild digestive complaints such as bloating.
Turmeric
Relief of digestive disturbances such as a feeling of fullness and flatulence.
Liquorice
Digestive complaints including burning sensation and dyspepsia; and as an expectorant in cough associated with a cold.
Milk thistle
Relief of digestive complaints, including a feeling of fullness and indigestion.
Keep the whole list in one place
TempoLife logs supplements alongside food, sleep and how you actually felt — so the answer to "what are you taking?" is a screen, not a guess.