Fennel seed is widely used in India as an after-dinner mouth freshener and also as a promoter of digestion. It is used as an important component in essential oils. It is a great boon to women as it balances their blood pressure, enhances libido, promotes lactation, and hastens menstruation. Health benefits of fennel. 1) Fennel, a great boon to increase libido. Fennel stimulates the effects of estrogen and fennel tea has traditionally been used to treat premenstrual syndrome, poor lactation, menopausal symptoms, and low libido. Fennel can relax the smooth muscles in the uterus and relieve menstrual cramps.