Vitex Berries have been used for centuries to treat constipation, flatulence, and hangovers, and to bring on menstruation and lactation. In modern herbal medicine, the herb is mainly used to treat breast swelling and breast pain caused by excessive secretion of the hormone prolactin during PMS or cyclic mastalgia. The herb can lengthen the proliferative (first) phase of the menstrual cycle, and also relieve water weight, headache, and fatigue.