Black cohosh is an herb showing increased use by women for the treatment of menopause symptoms, including hot flashes, night sweats, and vaginal dryness. Some research indicates that black cohosh may have an effect on hormone levels, which could be its mechanism of action.
Few side effects have been reported with the use of black cohosh, and those reported were generally mild, including headache, upset stomach, weight gain, and dizziness.
Liver damage has been reported in a few individuals taking black cohosh, although there is not sufficient research to determine whether the damage was caused by the herb. As a precautionary measure, however, those with liver conditions should not take black cohosh.
Because it may be estrogenic, or have other effects on hormone levels, those who have or at risk for breast cancer or uterine cancer should not take black cohosh.
Those who are pregnant or planning to become pregnant should not use black cohosh, due to increased risk of miscarriage. Breastfeeding mothers also should not use black cohosh, as adequate research has not been conducted as to the safety for very young children.
Long-term safety has not been evaluated, and black cohosh is not recommended for use for more than 6 months.