Cupping set, London, England, c. 1860-1875. Cupping was a method of bloodletting, a practice once carried out to treat a wide range of diseases and medical conditions. Warm glass cups were placed on the skin to draw blood believed to be harmful to health to the surface of the skin. In wet cupping, the blood was released from the body using a lancet or scarificator (a set of spring-operated lancets).