It may seem counterintuitive to consider the medicinal properties of arsenic, given its notoriety as a poison, but it has been used as a medicine for a long time. There are more than 200 naturally occurring minerals containing arsenic, and the ancient Greeks, including Hippocrates, used some of these for medicinal purposes. In Europe in the sixteenth and seventeenth centuries, red and white arsenic was packed into amulets and worn around the neck to ward off the plague. In the 1800s, the “arsenic eaters” of Styria believed that taking arsenic could prevent disease and improve complexion, endurance and libido. Throughout the 1800s, Fowler’s Solution, containing arsenic trioxide, was popular for the treatment of a wide variety of disorders. The British Pharmaceutical Codex of 1907 had about 60 references to arsenic and its applications for treating rheumatism, epilepsy, syphilis and more. The use of arsenic peaked in the early twentieth century with the discovery of an arsenic-based cure for syphilis, which was used until the discovery of antibiotics. Traditional Chinese medicine assisted in the discovery of arsenic as a treatment for a serious and difficult-to-treat form of leukemia. Arsenic also played a role in the treatment of sleeping sickness and in veterinary medicine.