Mustard agent, or
sulphur mustard, commonly known as
mustard gas, is a class of related
cytotoxic and
vesicant chemical warfare agents with the ability to form large
blisters on the exposed skin and in the lungs. Pure sulfur mustards are colorless, viscous liquids at room temperature. When used in impure form, such as warfare agents, they are usually
yellow-brown in color and have an odor resembling
mustard plants,
garlic, or
horseradish, hence the name. Mustard agent was originally assigned the name LOST, after the scientists Wilhelm Lommel and
Wilhelm Steinkopf, who developed a method for the large-scale production of mustard agent for the
Imperial German Army in 1916.