Ablister agent (orvesicant) is a chemical compound that causes severe skin, eye and mucosal pain and irritation in the form of severechemical burns resulting in fluid filled blisters.^[1] Named for their ability to causevesication, blister agent refers in common parlance to those agents which are developed for, or have been in the past utilized aschemical weapons, though some naturally occurringterpenoids such ascantharidin andT2 mycotoxin fall under this class.^[2] Exposure to blister agents is widely incapacitating, but often precipitates a delayed effect, with symptoms developing one to twenty four hours following the initial contact with the agent.^[3] Treatment for acute exposure is largely supportive, with the exception ofLewisite, for which an antidote is available.^[4] Overall lethality as a direct result of exposure is low, but increases with dose. Despite low overall lethality, blister agent exposure requires extensive supportive treatment, and can cause significant strain on medical systems.^[1][4][5] In some cases, blister agents have limited medical uses including for purposes of wart removal.^[2]

Blister agents relevant to warfare are generally divided into three categories:

• Mustards - A family of related agents whose odor is similar tomustard plants,garlic, orhorseradish, giving them their name.^[6] This family includes two primary subtypes:
  • Sulfur mustards – A subfamily ofsulfur-based agents, including what was referred to as mustard gas during World War I.
  • Nitrogen mustards – A subfamily of agents similar to the sulfur mustards, but based onnitrogen instead of sulfur, of which three varieties exist which are significant to warfare.^[7]
• Organoarsenics - A family of agents includingethyldichloroarsine (ED),methyldichloroarsine(MD) andphenyldichloroarsine (PD).^[8]
• Lewisite – An early blister agent that was developed, but not used, duringWorld War I. It was effectively rendered obsolete with the development ofdimercaprol in the 1940s.

Some sources erroneously reportphosgene oxime, anettle agent as a blister agent. Because it causesurticaria, not vesication, the grouping is not consistent with the accepted categorization of the blister agents.^[9]

Exposure to a weaponized blister agent can cause a number of life-threatening symptoms, including:

• Severe skin, eye and mucosal pain and irritation
• Skinerythema with large fluidblisters that heal slowly and may become infected
• Tearing,conjunctivitis,corneal damage
• Mildrespiratory distress to marked airway damage

All blister agents currently known are denser than air, and are readily absorbed through the eyes, lungs, and skin.^[5] Exposure to blister agents may precipitate a wide variety of long term effects due primarily to their general statuses ascarcinogens, and their abilities to cause permanent cellular damage.^[10]

• Medterms.comArchived 2012-08-09 at theWayback Machine
• Medical Aspects of Biological and Chemical Warfare, Chapter 7: Vesicants

• Blister agents

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