A new method to improve penetration depth of dyes into the follicular duct: Potential application for laser hair removal

Abstract

Background: Many persons seek to decrease hair growth and hair density. Although a variety of epilating methods are available, a practical and permanent hair removal treatment is needed. Objective: The purpose of this study was to evaluate a new method of obtaining a better penetration depth of dyes into the follicular duct. By increasing both the quantity and the penetration depth of dye into the follicular duct, the efficacy of laser hair removal could be improved. Methods: Dye penetration depth was assessed histologically after the use of formulations containing rhodamine-6G-loaded microspheres dispersed into two different silicones. Each formulation was tested on two hairless rats. After formulation application, dye diffusion was realized by applying ethanol on the skin to extract rhodamine-6G from microspheres. Results: In all our experimental conditions follicular targeting occurred. No difference in the penetration depth of rhodamine-loaded microspheres was seen between our different silicone formulations. After ethanol application, the penetration of rhodamine-6G into the hair follicle was considerably increased by the fluid silicone vehicle (vs volatile silicone). Conclusion: This new galenical approach aims to transport a dye into the hair follicle specifically and deeply. By using adequate laser, the efficiency of laser hair removal could be increased. (J Am Acad Dermatol 1999;41:172-5.)