Black cohosh is a plant. The underground stem of this plant is available in powder, tablet, or liquid form.
People most often take black cohosh for menopausal symptoms (such as hot flashes, night sweats, mood swings, rapid heart rate, and vaginal dryness). People sometimes take black cohosh to treat arthritis, to induce labor, or to treat menstrual symptoms.
Scientific evidence regarding benefit in relieving menstrual symptoms is conflicting. There are few reliable data on the effectiveness of black cohosh for other disorders and symptoms.
Side effects are uncommon. The most likely are headache and stomach discomfort. There is no evidence that black cohosh interferes with any drugs.
Black cohosh may cause headaches, dizziness, excessive sweating, nervous system problems, and vision disturbances (if high doses are taken). Other side effects include low blood pressure, constipation, loss of bone mass, muscle damage, digestive tract discomfort, liver toxicity, reduced pulse rate, nausea, and vomiting.
People who are sensitive to aspirin or have a seizure disorder, liver disease, hormone-sensitive cancers (for example, certain kinds of breast cancer), stroke, or high blood pressure probably should not take black cohosh. The U.S. Pharmacopeia (USP) has recommended that black cohosh products should be labeled with a warning declaring that they may be toxic to the liver.