The essential oil contains anethole (50 to 80%), limonene (5%), fenchone (5%), estragole (methyl-chavicol), safrole, a-pinene (0.5%), camphene, b-pinene, b-myrcene and p-cymene. The seed also contains fiber and complex carbohydrates.

Fennel seed teas are helpful for colicky infants, but fennel seed oil should never be given to infants or young children because of the danger of spasms of the throat.

Fennel is an excellent stomach and intestinal remedy that relieves flatulence and colic while stimulating digestion and appetite.  It is similar to aniseed in its calming effect in bronchitis and other coughs, and is a good choice for flavoring cough remedies.  Fennel may increase milk flow in nursing mothers. Used externally, the essential oil eases muscular and rheumatic pains.  Fennel infusion may be used as a compress to treat conjunctivitis and blepharisits (inflammation of the eyelids).* David Hoffman Medical Herbalism