Black cohosh is a plant. The underground stem of this plant is available in powder, tablet, or liquid form. Black cohosh should be manufactured to contain certain active ingredients, called triterpenes. Black cohosh contains certain ingredients, such as a form of aspirin, that provide anti-inflammatory effects. Although it is used to produce estrogen-like effects, it does not contain any plant estrogens.
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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 or to treat menstrual symptoms.
Scientific evidence regarding benefit in relieving menopausal symptoms is conflicting. For example, black cohosh may help relieve menopausal symptoms but not as effectively as hormonal treatments. 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.
Black cohosh may also cause dizziness, excessive sweating, nervous system problems, and low blood pressure (if high doses are taken).
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.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health (NIH), National Center for Complementary and Integrative Health: General information on the use of black cohosh as a dietary supplement