Dichloroethyl sulfide is a toxic chemical warfare agent that is commonly known as mustard gas. There are several synonyms for this chemical compound, including bis(2-chloroethyl) sulfide, mustard compound, and sulfur mustard. Mustard gas is a potent blistering agent that has been used in warfare since World War I. It causes severe skin burns, respiratory damage, and can lead to death in high doses. The use of mustard gas is prohibited by international law, but it remains a threat as a chemical weapon. The development of effective treatments and protective measures against it is therefore crucial.