Characterization of the mineral content of a physical sunscreen emulsion and its distribution onto human stratum corneum.

When using physical sunscreens, protection and aesthetic aspects are directly related to particle size and mineral distribution onto skin. These investigations aimed to characterize the different mineral raw materials entering into the composition of a specific sunscreen emulsion and to assess the distribution of the sunscreeen agents at the surface of human stratum corneum. X-ray diffractometry revealed the crystallographic features of the TiO2 and ZnO crystals. Frequency distributions of crystal length and aspect ratio were determined for the zinc oxide which presented the largest particle size and varying shapes. Scanning and transmission electron microscopy disclosed structural information. The results reported in this study specify the characteristics of the oxide particles involved in the formulation and show a satisfactory mineral distribution along the irregular topography of the skin. No intracellular penetration was noted.