Black cohosh is a tall perennial herb originally found in the northeastern United States. Native Americans used it primarily for women's health problems, but also as a treatment for arthritis, fatigue, and snakebite. European colonists rapidly adopted the herb for similar uses. In the late nineteenth century, black cohosh was the principal ingredient in the wildly popular Lydia E. Pinkham's Vegetable Compound for menstrual cramps.

Black cohosh’s main use today is for the treatment of menopausal symptoms. Meaningful but far from definitive evidence indicates that black cohosh extract might reduce hot flashes as well as other symptoms of menopause.

In the past, black cohosh was believed to be a phytoestrogen, a plant-based substance that has actions similar to estrogen. However, as we describe below, growing evidence indicates that black cohosh does not have general estrogen-like actions. Rather, it may act like estrogen only in certain places: the brain (reducing hot flashes), bone (potentially fighting osteoporosis), and vagina (reducing vaginal dryness).

Black cohosh has also been tried for reducing hot flashes in women who have undergone surgery for breast cancer, but it does not appear to be effective for this purpose.

Finally, black cohosh is sometimes recommended as a kind of general women’s herb, said to be effective for a variety of menstrual issues, such as dysmenorrhea, premenstrual syndrome (PMS), and irregular menstruation. However, there is as yet no meaningful evidence at all that the herb is effective for these conditions.