Bruising and Bleeding. Bruising or bleeding after an injury is normal. However, some people have disorders that cause them to bruise or bleed too easily. Sometimes people bleed without any obvious triggering event or injury.
The skin of victims of mustard gas blistered, the eyes became very sore and they began to vomit. Mustard gas caused internal and external bleeding and attacked the bronchial tubes, stripping off the mucous membrane. This was extremely painful and most soldiers had to be strapped to their beds.
It is more harmful to the skin on hot, humid days or in tropical climates. Mustard gas was used in chemical warfare in World War I and World War II. It was so powerful. that only small amounts had to be added to explosives for it to be effective.