Apiaceae

Foeniculum vulgare

Fennel

Mixed Caution

Part used: seedrootaerial
Native range: Mediterranean; naturalised aggressively worldwide including across southern Australia
Morphology: A tall aromatic perennial to two metres with hollow ridged stems, very finely divided thread-like leaves, and broad umbels of small yellow flowers followed by ridged aromatic seeds.

What is in it

volatile oil anethole, fenchone, estragole

flavonoids

Evidence

Some trial support for infant colic in combination preparations and for dysmenorrhoea. Lactation claims are traditional and not established.

Safety

Culinary use is benign. Estragole is a recognised genotoxic carcinogen in animal studies, which is why regulators limit fennel-oil exposure and advise against prolonged high-dose use, particularly in infants and pregnancy. The EMA advises against fennel tea in children under four.

Interactions: Oestrogenic activity reported; caution in hormone-sensitive conditions; May reduce absorption of ciprofloxacin

Regulatory: Permitted as a food. Regulatory advice restricts prolonged use in infants and in pregnancy.

How the traditions classify it

Galenic Hot and dry in the second degree. Used for the eyes, for digestion and to promote milk.

Chinese Xiao hui xiang — pungent and warm, for cold in the lower abdomen.

Ayurvedic Sweet and pungent, cooling in potency, and chewed after meals for digestion.

Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.

Historical use

Recorded in every major European source, used for digestion, colic, eyesight and lactation, and chewed to suppress hunger during fasts. The seeds are a standard after-meal digestive across South Asia.

Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.

Worth knowing

Fennel is the clearest example of a wholly ordinary kitchen plant carrying a genuine regulatory concern, and of the concern being about duration rather than dose.

Estragole is genotoxic in animal studies. Nobody thinks a fennel seed after dinner matters. What the European regulators worried about was fennel tea given daily to infants for colic over months — a small exposure, repeatedly, to the group with the least capacity to handle it. The resulting advice against fennel tea under the age of four surprises people precisely because the plant is so familiar.

Nomenclature verified against GBIF backbone taxonomy.