are no greater than those variations seen in the different body regions of a single individual. According to Nagy and colleagues (1946), there is no difference in the rate of sulfur mustard penetration between the skin of whites and blacks. It is suggested that well-designed contemporary studies are needed to better define the resistance or susceptibility of specific skin thicknesses and types to injury.
The most useful clinical descriptions of acute sulfur mustard effects on human skin have been reported by Momeni and colleagues (1992), Smith and Dunn (1991), and a group of clinicians at the Hospital of the University of Ghent Medical School, Belgium (Willems, 1989). These reports were based principally on the examination of patients and patient records of individuals exposed to sulfur mustard during the Iran-Iraq conflict of 1980-1988.
Gross morphologic changes in the skin induced by sulfur mustard are characterized by the appearance of an intense period of itching followed by erythema and edema (signs of inflammation), as well as blister (vesicle) formation, denudation of skin, ulceration, and necrosis. Immediate color changes are often described in affected skin and occur in response to stimulation of melanogenesis, probably an effect akin to the "immediate darkening" effect seen after a specific type of acute UV exposure, and from the darkening effect of "cooked" protein within epidermal cells. Increased darkening of the skin from increased melanogenesis at the periphery of mustard-induced blisters is also characteristically observed. Peripheral darkening is often associated with larger areas of hyperpigmented skin that occur at sites where erythema and edema without previous blister formation had existed. Exfoliation and deep ulceration may occur at these sites. Tissue dosages of sulfur mustard vapor required to induce erythema vary between 0.1 and 1 mg/cm2. Vesication can be expected in 50 percent of a population at tissue dosages of 1-2 mg/cm2.
It should be remembered that the site of exposure may be associated with variations in the skin's response to the same amount and extent of sulfur mustard exposure. At the same dosage and time of exposure, loose tissue (less compact dermis) as seen on the face, especially around the eye, and on the genitalia may respond with edema without blistering. However, tissue sites having a very dense dermis, as on the back, may respond with erythema and blister formation without edema.
Healing of the skin is variable and, in the absence of secondary bacterial infection, may proceed without residual defects. The minimally injured hair follicles and other adnexal structures contribute greatly to the healing wound. Tissue reepithelialization often begins and spreads