List of Black Cohosh Adverse Effects

Women often take black cohosh or Actaea racemosa to treat menstrual and menopausal problems, such as hot flashes, although there is no definitive scientific evidence of its effectiveness. Black cohosh, which is native to North America, has no significant drug interactions, but can have mild side effects in some people. Moderate side effects are rare, but occur in higher doses.



Pregnant women should never take black cohosh due to the risk of miscarriage. Because of its estrogenlike properties, black cohosh can diminish the effectiveness of birth control pills. People who are allergic to members of the Ranunculaceae plant family should avoid black cohosh since it may cause an allergic reaction. Liver damage and liver failure have been reported in rare cases, according to the National Institutes of Health. Consult a doctor before taking black cohosh while breastfeeding.

Infrequent, Mild, Adverse Effects

• Women may experience gastrointestinal discomfort, such as stomach aches and constipation, when taking black cohosh. Other mild, adverse effects reported include heaviness in the legs. These mild side effects may occur even when the person takes the recommended dosage. The National Institutes of Health report few adverse effects have been documented.

Rare, Adverse Effects

• Some of the rare, adverse effects occur when black cohosh is taken in large doses. Rare, adverse effects include sweating, low blood pressure, slow heartbeat, weight gain, dizziness, giddiness, nausea, headaches and vomiting. The adverse effects may occur when black cohosh is taken in large quantities by women trying to self-medicate without medical supervision.

Adverse Effects of Mixing

• Black cohosh should not be mixed with acetaminophen. Black cohosh, which contains salicylates, should not be taken with other salicylates--such as Aspirin or blood-thinning medicines--due to the risk of bleeding. Because black cohosh can lower blood pressure, it should not be taken by people on Lopressor, Toprol or drugs that lower blood pressure. Black cohosh can increase the side effects that come with taking Tamoxifen or Nolvadex, a cancer drug.