Medically reviewed on June 7, 2018
What is Fennel?
Fennel is an herb native to southern Europe and Asia Minor. It is cultivated there, and in the US, Great Britain, and temperate areas of Eurasia. All parts of the plant are aromatic. When cultivated, fennel stalks grow to a height of about 1 m. Plants have finely divided leaves composed of many linear or awl-shaped segments. Grayish compound umbels bear small, yellowish flowers. The fruits or seeds are oblong, oval shaped, about 6 mm long, and greenish or yellowish brown in color with 5 prominent ridges. The seeds have a taste similar to anise. Foeniculum dulce (carosella) is grown for its stalks, while F. vulgare (finocchio) is grown for its bulbous stalk bases. A number of subspecies have been identified.
Common fennel, sweet fennel, bitter fennel, carosella, Florence fennel, finocchio, garden fennel, large fennel, wild fennel
What is it used for?
According to Greek legend, man received knowledge from Mount Olympus in the form of a fiery coal held in a stalk of fennel. The herb was known to the ancient Chinese, Indian, Egyptian, and Greek civilizations; the Roman scholar Pliny recommended it for improving eyesight. The name foeniculum is from the Latin word for "fragrant hay." Fennel was in great demand during the Middle Ages. Wealthy people added the seed to fish and vegetable dishes, while the poor reserved it as an appetite suppressant to be eaten on fasting days. The plant was introduced to North America by Spanish priests and the English brought it to their early settlements in Virginia. All parts of the plant have been used for flavorings, and the stalks have been eaten as a vegetable. The seeds aid digestion. Fennel has been used to flavor candies, liqueurs, medicines, and food, and it is especially favored for pastries, sweet pickles, and fish. The oil can be used to protect stored fruits and vegetables against growth of toxic fungi. Beekeepers have grown it as a honey plant. Health claims have included its use as a purported antidote to poisonous herbs, mushrooms, and snakebites. It also has been used for the treatment of gastrointestinal inflammation, indigestion, to stimulate milk flow in breast-feeding, as an expectorant, and to induce menstruation. Tea made from crushed fennel seeds has been used as an eyewash. Powdered fennel is said to drive fleas away from kennels and stables.
Fennel has been used as a flavoring agent, a scent, and an insect repellent, as well as an herbal remedy for poisoning and stomach conditions. It has also been used as a stimulant to promote milk flow in breast-feeding and to induce menstruation. However, clinical evidence to support the use of fennel for any indication is lacking.
What is the recommended dosage?
Fennel seed and fennel seed oil have been used as stimulant and carminative agents in doses of 5 to 7 g and 0.1 to 0.6 mL, respectively.
Contraindications have not yet been identified.
Documented adverse reactions and menstruation induction effects. Avoid use.
One study suggested that a fennel constituent has the ability to inhibit the drug metabolizing enzyme cytochrome P450 3A4. Therefore, fennel should be used cautiously with medications metabolized by this enzyme.
Fennel may cause sun poisoning, skin reactions, and cross reactions. The oil may cause hallucinations and seizures. Premature breast development in girls has been reported with the use of fennel. Poison hemlock may be mistaken for fennel.
Fennel oil was found to damage DNA. Estragole, present in the volatile oil, has been shown to cause tumors in animals.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.