vesicant

Vesicants, also called blister agents, are a class of toxic chemical warfare agents that cause blistering and tissue injury on contact with skin or mucous membranes. They are typically persistent liquids or semi-volatile compounds that can be released as liquids, mists, or vapors and may remain hazardous in the environment for varying periods, depending on light, temperature, and soil conditions. The best-known vesicants include sulfur mustard and nitrogen mustards, with Lewisite and phosgene oxime also classified as vesicants.

Mechanism and effects: Vesicants damage tissues primarily through alkylation of cellular components, leading to cell death and separation of epidermal layers. Skin exposure produces erythema and delayed blistering (vesication) within hours to a day; eyes can suffer conjunctival irritation and corneal injury; inhalation can cause inflammation of the airways and, in severe cases, pulmonary edema. Systemic toxicity may occur with certain agents such as Lewisite, which also contains arsenic.

Examples and regulation: Sulfur mustard is a sulfur-containing alkylating agent; nitrogen mustards have similar properties. Lewisite is arsenic-based and more acutely toxic via inhalation and skin contact; phosgene oxime is a fast-acting vesicant. Vesicants are prohibited in warfare under the Chemical Weapons Convention and are subject to international control and national regulatory measures.

Treatment and safety: Medical management emphasizes rapid assessment and supportive care, with a focus on preventing secondary infection and treating eye and airway injuries. For some vesicants, specific chelation therapy may be considered for arsenic-containing agents. There is no universal antidote for most vesicants; protection and swift medical attention are essential.