Known as Cimicigufa racemosa and Actaea remosa, black cohosh has been use by some women to deal hot flashes. Black cohosh is usually sold as a dietary supplement. But the reason why is it so effective is still unknown to researchers. According to the American College of Obstetrician and Gynecologist, the effectiveness of black cohosh for hot flashes can last six months or more for women displaying menopausal symptoms. Though it's a natural remedy, black cohosh also has few side effects. Report says that few women experience gastric discomfort, but only for a short time.