Laser spectroscopic methods for the characterization of open and closed follicles

Hair follicles have been assigned an increasingly significant role in dermatopharmacology. Previous studies have shown that the penetration of substances into the follicle depends on its activity. Telogen follicles that were not producing sebum were closed for follicular penetration. The present study uses optical coherence tomography (OCT) to show that the orifices of inactive follicles are blocked by plugs formed of corneocytes. The follicular penetration of a fluorescent dye was analyzed by cyanoacrylate surface biopsies in combination with laser scanning microscopy. Surface exfoliation and cyanoacrylate surface peels were used as a pre-treatment to remove the corneocyte plugs from the follicular orifices and therefore to open up closed follicles. It was shown that both procedures could increase the number of open hair follicles significantly. The present experiments show that OCT in combination with laser scanning microscopy is an excellent non-invasive in vivo method for the investigation of hair follicle properties and follicular penetration processes.