autonomic-nervous-system regulation, nightmares, headache, drowsiness, dizziness, anxiety, apathy, confusion, restlessness, emotional lability, anorexia, insomnia, lethargy, inability to concentrate, memory deficits, depression, irritability, generalized weakness, and tremors as well as subtle electroencephalographic changes This syndrome can be difficult to differentiate from posttraumatic stress disorder (PTSD) but appears to be distinct from it Vesicants The major vesicants, or blistering agents, are cellular poisons and include the mustards (sulfur mustards and nitrogen mustards) and Lewisite The mustards act primarily as alkylating and inflammatory agents, whereas Lewisite is an organic arsenical believed to affect the thiol groups in critical cellular enzymes Because little clinical experience with Lewisite exposure exists, this discussion focuses on mustard Mustard exists as an oily, yellow to dark brown liquid with a garlic, mustard, or “hot asphalt” odor It may vaporize at high temperatures, and mustard vapor, unlike most other chemical vapors, can penetrate skin and lead to early tissue damage and eventual blistering, thus warranting emergent skin decontamination Mustard forms a cyclic ethylsulfonium ion that is a potent alkylating agent binding to DNA and other cellular constituents and causing injury to rapidly reproducing cells with local effects most evident on the skin and in the eyes and respiratory tract With severe exposures, the bone marrow, GI mucosa, and the CNS may also be damaged Although mustard-induced cell injury begins within the first few minutes after exposure, clinical effects of mustard usually follow a latent period of up to to hours that is inversely related to dose Skin lesions after liquid contact begin with erythema, followed by blister formation; after large doses there is skin sloughing without blister formation ( Fig 132.8 ) The burns are usually of partial thickness A “string-of-pearls” distribution of blisters is sometimes seen to surround a central area of normal-appearing skin; in truth, the central area is too injured to form vesicles Blister fluid does not contain active mustard and is not hazardous