In this study, several cosmetic urea formulations containing phospholipids, a charge inducer with or without cholesterol (liposomes) and a non-ionic surfactant, a charge inducer with cholesterol (niosomes), were investigated, We used comparable liposome and niosome formulations from various phospholipids and surfactants to investigate whether gel and liquid crystalline state vesicles differ in their effect on skin hydration. Gel state liposomes and niosomes, liquid crystalline state liposomes and niosomes were prepared. The film method was used, followed by sonication and extrusion through a polycarbonate membrane. The particle size distribution, entrapment efficiency, content of phospholipid and bilayer type and composition stability were determined. In vitro release of urea was investigated at 37 degrees C, 35 r/min in 10 mM Tris (pH 7.4) buffer In vitro release was investigated and its fit to kinetic models was evaluated. All vesicles were labelled by Tc-99m and applied topically to the back of guinea pigs. The biodistribution was compared with that of a commercial product. The same formulations were applied to human volunteers. The moisturizing effect was determined by Sebutest based on the differing dielectric constants of water and other substances. In this study, skin humidity could be increased and accumulation of urea-loaded vesicles in the stratum corneum could be demonstrated. No particular affinity of the phospholipids/surfactants for the deeper-lying skin tissues could be demonstrated.