From Wikipaedia. "Cansema (also known as black salve) is a brand name of a popular alternative cancer treatment. The product is commonly classified as an escharotic—that is, a topical paste which burns and destroys skin tissue and leaves behind a thick, black scar called an eschar. Escharotics were widely used to treat skin lesions in the early 1900s, but have since been replaced by safer and more effective treatments. Escharotics such as Cansema are currently advertised by some alternative medicine marketers as treatments for skin cancer, often with unsubstantiated testimonials and unproven claims of effectiveness. The U.S. Food and Drug Administration has listed Cansema as a "fake cancer cure" and warns consumers to avoid it. Cancer salves were first documented as a form of quackery in a 1955 Time article: A 37-year-old housewife had a skin condition that later (at Duke) proved not to be a cancer. Convinced that it was, she had gone to a backwoods healer, who applied a salve. Soon a quarter-sized hole disfigured her nose, opened up the nasal cavity. Duke's plastic surgeons had to build her a new nose. More recent reports document the ongoing marketing of escharotics via the Internet as purported "cures" for skin cancer.
Cansema and other escharotics are not recommended as treatments for skin lesions or skin cancer. The effectiveness of escharotics is unproven, and much safer and more effective alternatives exist, such as Mohs surgery. Escharotics can cause serious scarring and damage to normal skin. Their manufacture is largely unregulated, so the strength and purity of marketed products are unknown and unverified. Numerous reports in the medical literature describe serious consequences of using escharotics in place of standard treatments for skin cancer, ranging from disfigurement to preventable cancer recurrences. The website Quackwatch posted a warning against the use of escharotics in 2008. The site collected a variety of sourced documents compiling issues of patient injury from the use of escharotics. Common ingredients of black salves include zinc chloride and chaparral, also known as creosote bush (Latin name Larrea tridentata)and often bloodroot, a plant which has numerous uses in herbal medicine. The extract of bloodroot is called sanguinarine, an ammonium salt which attacks and destroys living tissue and is also classified as an escharotic."