Awaiting clinical review. This entry is sourced but has not yet been signed off by a pharmacist or clinician.

Foeniculum vulgare (fruit/seed)

Fennel

Fennel seed has the best modern evidence for period pain and infant colic, where small trials mostly favour it, but the studies are small, vary a lot and carry a risk of bias, so it rates as limited rather than proven. For bloating and wind the case rests on traditional use, backed by one small trial. The main caution is estragole, a compound in fennel: the EU regulator advises against fennel tea in children under 4 and in pregnancy and breastfeeding.

Written by

Healthy and Herbal editorial team

Updated

29 September 2026

At a glance

Last reviewed 29 September 2026

Evidence

Limited

Best for

Period pain

Typical form & use

Seed tea, 1.5 g three times daily

Onset

4+ weeks

Safety

Avoid in pregnancy and under 4s (estragole). No interactions in our data.

Check with your medications →

What it's used for

Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.

Use	Evidence	What the research shows
Period pain (primary dysmenorrhoea)	Limited	A 2020 meta-analysis of 12 trials found fennel similar to conventional painkillers (SMD 0.07, 95% CI −0.08 to 0.21, n = 502) and better than placebo (SMD −3.27, 95% CI −5.28 to −1.26), but with I² of 98% and signs of publication bias from many small favourable studies. A 2021 meta-analysis found a smaller placebo effect (SMD −0.63, 95% CI −0.83 to −0.44, seven articles) and again no clear difference from mefenamic acid. Both agree on the direction; they disagree on the size, and the trials are small. The EU regulator recognises fennel fruit tea for minor menstrual spasm on traditional use alone.^1,2,7
Infant colic	Limited	A placebo-controlled trial in 125 infants found colic resolved in 65% given fennel seed oil emulsion versus 23.7% given placebo. A review pooling three trials of fennel-containing preparations found crying was 72 minutes a day shorter (95% CI −126 to −18). The Cochrane review, which covered one fennel, chamomile and lemon balm combination trial (93 infants), rated the evidence very low quality and could not recommend any dietary intervention. The EU regulator does not recommend fennel tea under 4 years of age because of a lack of adequate data.^3,4,5,7
Bloating and wind	Traditional	The EU regulator recognises fennel fruit tea for mild spasmodic gut complaints including bloating and flatulence, based on long-standing use only. The one trial we found, in women after caesarean section, showed fennel capsules reduced flatulence about as much as dimethicone, but it had no placebo group and was in a very specific setting. We found no placebo-controlled trial of fennel alone for everyday bloating.^6,7

How much

Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.

EU monograph, adults

1.5 g seed in 250 ml, 3 times daily^7,8

Steep in boiling water for 15 minutes. That is 4.5 g a day. The same dose is listed for bloating and for minor period cramps, for adults and adolescents.

Children 4–12 years

1 g seed in 100 ml, 3 times daily⁷

Bloating and wind only, for less than a week. The regulator advises against use if estragole intake would exceed 1.0 µg per kg of body weight a day. Period pain use under 12 has not been established.

Under 4 years

Not recommended^7,3

The EU regulator cites a lack of adequate data. The infant colic trials tested a seed oil emulsion and a herbal mixture, not home-made fennel tea, so they do not set a safe home dose.

Duration

No more than 2 weeks (adults)⁷

The EU monograph's limit for traditional use in adults and adolescents. Long-term safety is not established.

Timing · The monograph gives three daily doses and no timing advice. For period pain, the trials we reviewed at summary level treated pain over cycles, so we did not extract a start day.With food? · No source we read gave food guidance. Fennel tea is traditionally drunk after meals, but that is custom rather than evidence.How long to trial · For bloating, a short spell is enough to tell. For period pain, judging over one or two cycles is reasonable. If symptoms persist or worsen, the EU monograph advises seeing a doctor or qualified practitioner.

How people take it

Seed tea (infusion)1.5 g in 250 ml, 3 times daily (adults)The form the EU monograph covers. Bitter and sweet fennel fruit have separate monographs with matching dosing. Estragole content varies between batches.

CapsuleVaries by product; follow the labelUsed in the trials of period pain and post-caesarean wind. We did not extract doses, and products are not interchangeable.

Seed oil emulsion (infants)Clinician-directed onlyThe form tested in the infant colic trial. Not a product for parents to make up, and we did not verify a dose.

Safety

Who should avoid

Children under 4 — EU regulator does not recommend fennel tea, too little data
Pregnancy and breastfeeding — EU regulator advises against; estragole limits apply
Allergy to celery, aniseed, caraway, coriander or dill — cross-reactivity
Allergy to mugwort pollen — cross-reacts with fennel
Heavy, prolonged or worsening period pain — needs assessment, not a herb

Known interactions

No interactions in our data. Absence of a flag is not clearance.

Questions people ask

Does fennel tea help with period pain?

Two meta-analyses found fennel reduced period pain and worked about as well as painkillers such as mefenamic acid. The trials were small and varied widely in size of effect, and there were signs of publication bias, so treat it as promising rather than proven.

Is fennel safe for babies with colic?

The evidence is not strong enough to be sure. Small trials of fennel oil emulsion and a fennel herbal mixture reported less crying with no side effects, but the Cochrane review rated the evidence very low quality. The EU regulator does not recommend fennel tea under 4 years because of estragole and a lack of data, so speak to a health visitor or GP before giving a baby anything.

What is estragole and why does it matter?

Estragole is a natural compound in fennel fruit that causes liver tumours in mice at high doses. The EU regulator sets an intake limit of 1.0 µg per kg of body weight for children under 12 and 0.05 mg a day in pregnancy and breastfeeding, and says exposure should be kept as low as practicable for everyone.

Does fennel help with bloating and wind?

It is a traditional remedy recognised by the EU regulator for mild spasmodic gut complaints, but we found no placebo-controlled trial of fennel alone for everyday bloating. One small trial after caesarean section found it worked about as well as dimethicone.

Sources

Last reviewed 29 September 2026 · Next review March 2027 · How we rate evidence