Investigation of differences in follicular penetration of particle-and nonparticle-containing emulsions by laser scanning microscopy

The study investigated the penetration of particle- and nonparticle-containing emulsions into hair follicles using laser scanning microscopy. It was found that particles with a size similar to the thickness of keratin cells in hair penetrated more efficiently into hair follicles. This was attributed to the movement of hairs within the follicles, which acted as a geared pump due to the zigzag structure of the hair surface, effectively pushing particles of the corresponding size deep into the follicles. These findings were based on both in vitro and in vivo investigations.