Dose-Response of Human Follicles During Laser-Based Hair Removal: Ex Vivo Photoepilation Model with Classification System Embracing Morphological and Histological Features

The study aimed to develop an ex vivo photoepilation model to evaluate the response of human hair follicles (HFs) to light pulses and investigate their dose-response behavior. Human anagen HFs were treated with a single pulse of 810 nm light at fluences ranging from 1.7 to 26.4 J/cm² and maintained in culture for 7-10 days. The response was assessed through gross morphology and histological examination. The results showed a dose-dependent response with five distinct classes based on macroscopic and microscopic criteria. Fluences below 13.2 J/cm² induced a catagen-like transition, while higher fluences caused coagulation in HF compartments. The model provided a quick and effective method to predict the clinical efficacy and permanency of light-based hair removal devices.