This species is an annual or biennial plant of the Asteraceae family. This fairly typical thistle has red to purple flowers and shiny pale green leaves with white veins.

Milk thistle has been used for a number of purposes including liver disease, and cancer; however, clinical studies are largely heterogeneous and contradictory. Silybum marianum is used in traditional Chinese medicine to clear heat and relieve toxic material, to soothe the liver and to promote bile flow. Though its efficacy in treating diseases is still unknown, Silybum marianum is sometimes prescribed by herbalists to help treat liver diseases (cirrhosis, jaundice and hepatitis). Both in vitro and animal research suggest that Silibinin (syn. silybin, sylimarin I) may have hepatoprotective (antihepatotoxic) properties that protect liver cells against toxins.

Because of potassium nitrate content, the plant has been found to be toxic to cattle and sheep.