Possible side effects of black cohosh include seizures, rash, upset stomach, and skeletal or muscle conditions. Some people may experience abnormal vaginal discharge, chest discomfort, headache and heart problems. Other possible side effects include unhappiness, tiredness, nausea and overgrowth of the uterine lining, according to Mayo Clinic.
Additional potential side effects of black cohosh include altered blood pressure, irregular heartbeat, hepatitis and heaviness in the legs. Some people may experience liver damage, irritability, breast tenderness or skin lesions. Other possible side effects include visual disturbances, dizziness, vomiting and stimulation of menstrual flow. If a pregnant woman takes black cohosh, the infant may experience damage to multiple organs, notes Mayo Clinic.
Those who take medications or supplements to lower blood pressure should exercise caution when taking black cohosh, as it may lower blood pressure. People with conditions related to hormones should speak to a physician before using black cohosh. People who are allergic to plants in the Ranunculaceae family should avoid black cohosh, recommends Mayo Clinic.
People who are allergic to aspirin or other salicylates should be cautious when taking black cohosh, as black cohosh may contain trace amounts of salicylic acid. Because the FDA does not regulate herbs and supplements, it is important to be cautious when taking black cohosh products, states Mayo Clinic.