Fennel

Foeniculum vulgare · Fennel Seed · Fennel Extract

Snapshot

Indications	Contraindications
Infantile colic^{1, 2} Primary dysmenorrhea^{3, 4} Menopausal symptoms^5–8 Postoperative bowel recovery⁹ IBS symptoms (with fennel oil)¹⁰ Oligomenorrhea in polycystic ovary syndrome^11–15 Hirsutism, topical gel¹⁶	Apiaceae spice or pollen allergy¹⁷ Pregnancy¹⁸

Fennel (Foeniculum vulgare) seed and its essential oil are used for an antispasmodic and carminative effect on the gut. That effect underlies use for infant colic, postoperative bowel recovery, and irritable bowel symptoms. Fennel is also taken for menstrual pain and menopausal symptoms. Breastfeeding mothers use it as a galactagogue, where the evidence is very uncertain¹⁹. Typical users include postmenopausal women seeking relief from menopausal symptoms⁶.

Evidence is most consistent for infant colic, where a meta-analysis of fennel-containing preparations found shorter crying time. For dysmenorrhea, meta-analyses found pain reduction versus placebo and an effect similar to conventional analgesics^{3, 4}. A Cochrane review rated the evidence low quality and found no consistent benefit over placebo²⁰. A 2025 review of food supplements for digestive health found most claims for fennel-containing products rested on traditional use rather than clinical substantiation²¹. Products are teas, liquid extracts, capsules, and powders, with 1794 products listing fennel; see Form comparison.

Fennel shares allergens with birch and mugwort pollen and celeriac, so allergic reactions occur in pollen-allergic patients¹⁷. Per product labels, pregnant or nursing women and people taking medications are directed to consult a health care practitioner before use¹⁸.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

70 sources, 58 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources