Blistering Agent: the most dreaded of all chemical weapons in World War I - mustard gas. Unlike the other gases which attack the respiratory system, this gas acts on any exposed, moist skin. This includes, but is not limited to, the eyes, lungs, armpits and groin. The oily agent would produce large burn-like blisters wherever it came in contact with skin. It also had a nasty way of hanging about in low areas for hours, even days, after being dispersed. A soldier jumping into a shell crater to seek cover could find himself blinded, with skin blistering and lungs bleeding.