What Is the Difference between Black and Blue Cohosh?

Black and blue cohosh share a similar name. The word "cohosh" means "rough" in Algonquin, and it refers to how the roots look. The two herbs are from different plant families, and they bear little physical similarity to one another. Both herbs are used as herbal supplements, and they have some similar chemical properties, but they are used to treat different disorders.

Black cohosh plants, or Cimicifuga racemosa, grow 3-6 feet (91-183 cm) tall and have a bushy form. They are commonly called bugbane, black snakeroot and rattleweed, among other names. They produce elongated clusters of small white blossoms.

Blue cohosh, or Caulophyllum thalictroides, is also called papoose-root and squaw root. These spreading, shrubby plants grow 1-3 (30-91 cm) feet tall. They have multiple stems, greenish-yellow or brownish flowers and vivid blue berries.

The roots and rhizomes, or underground stems, of both black and blue cohosh are used in herbal preparations. People usually drink black or blue cohosh as an herbal tea. They might also use liquid extracts called tinctures or might swallow pills. Both black and blue cohosh might have estrogenic effects.

Some women use blue cohosh to regulate their menstrual cycles. The herb might also be useful in treating stomach cramps or constipation. Some midwives use blue cohosh alone or mix black and blue cohosh together to speed up the birthing process, but this practice is dangerous, because blue cohosh might cause heart problems in newborns.

American Indians have used black cohosh to treat sore throat, coughs, colds and rheumatism. In 2011, herbalists prescribed it to alleviate the symptoms of menopause, such as irregular menstrual cycles, vaginal dryness and hot flashes. It might also be useful as a remedy for arthritis pain.

Patients should use cohosh products only under the advice of a physician. Black cohosh might cause headaches and stomach upset in some individuals. In 2011, its long-term effects were unknown.

Blue cohosh might cause miscarriage in pregnant women. It might also increase a patient's blood pressure. Pregnant women and nursing mothers should avoid using either black or blue cohosh.

Some patients have experienced allergic reactions to blue cohosh. The symptoms of an allergic reaction include skin irritation; hives or rash; swollen tongue, lips or face; and respiratory distress. Patients who experience a severe allergic reaction should contact a physician immediately.

People who have liver disorders should avoid black cohosh. Women who have had breast cancer or who are undergoing treatment for estrogen-sensitive conditions should not use either product. Black and blue cohosh are unsafe for children.