Illustration showing brown staining of the skin from mustard gas. This staining appears in patients in areas that were first inflamed and red. This drawing was made on the eighteenth day after exposure to mustard gas. However, the brown staining first appeared on the sixth day after exposure to mustard gas. Exposure to mustard gas, a chemical warfare agent, can cause blistering of the skin and mucous membrane on contact. Mustard gas can also cause coughing and shortness of breath in the short term. It also has long term effects such as mouth, throat and skin cancer as well as leukaemia. Published in An Atlas of Gas Poisoning, 1918.