Black salve products have been widely advertised as an alternative medicine to treat a variety of dermatologic conditions including skin cancers, furuncles, nevi, and skin tags, among other conditions. The US Food and Drug Administration (FDA) has issued a warning that black salve is a dangerous product that is not approved to treat any of these skin conditions. It contains corrosive ingredients such as zinc chloride and sanguinarine (Sanguinaria canadensis, also known as bloodroot). These ingredients interfere with RNA and DNA gene expression and cell division, which leads to the inhibition of skin proliferation and subsequent necrosis.