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Severe exposure to HD induces blistering skin reactions and significant loss of stem cell keratinocytes that are required for a continuous renewal of the epidermal cell layer. Therefore, HD injuries require long healing periods leaving significant cosmetic and/or functional deficits. We are developing bioengineered skin from embryonic stem cells for improved therapy for HD-induced skin damage. Since stem cell keratinocytes lack major histocompatibility class II antigens, they exhibit little immunogenicity and are suitable for allograft use. The multipotential nature of stem cells may be particularly valuable for skin damage where several cell types and growth factors are necessary for proper repair and regeneration. We differentiated embryonic stem cells to skin keratinocytes in a cellular matrix cultured in an air/liquid system to form the bioengineered skin, mimicking normal skin. The efficacy of bioengineered skin for HD-induced skin lesions was evaluated using a C57BL/6 mouse model and 2-chloroethylethyl sulfide (half-mustard or CEES). Mice were exposed to 3 microliters neat CEES for 10 minutes, and at 48 h post exposure, the injured skin was excised and the site was cleaned with debridase. Next, the bioengineered skin was transferred directly to the wound and affixed with a non-adherent sterile gauze pad. The affixed with a non-adherent sterile gauze pad. The embryonic stem cell derived bioengineered skin exhibited growth and healing in 1 to 3 weeks. In contrast, the CEES exposed animals not treated with bioengineered skin had a) no skin growth and b) obvious contraction of the skin in the injured area. Our results demonstrate that for the first time, topically applied fresh or frozen bioengineered skin or skin keratinocytes from embryonic stem cells produce improved healing when applied 48 h after HD exposure., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, Florida on 27-30 November 2006. The original document contains color images.