The role of microtrauma in hair regrowth and regeneration in non-scarring alopecia.

Hair loss in both men and women significantly impact quality of life and often has modest treatment outcomes. Recently, microtrauma, which involves small, intentional skin injuries, has emerged as a promising method to stimulate hair growth through immunomodulation in non-scarring alopecias. This review explores the pathogenesis of hair loss, the mechanisms behind microtrauma, various methods of inducing it, and their efficacy in treating non-scarring alopecia. Hair follicles undergo cyclic phases of growth, regression, and rest, influenced by microenvironmental factors, including immune cells. Procedures utilizing microtrauma can promote hair regrowth by manipulating immune cells through wound healing responses, increasing growth factor release, and enhancing blood circulation. Examples of microtrauma include microneedling, fractional and non-fractional lasers, contact immunotherapy, low-level laser therapy (LLLT), and platelet-rich plasma (PRP) injections. Microneedling promotes stem cell activation and the expression of hair growth-related genes. Iontophoresis enhances drug delivery. Lasers induce controlled tissue injury leading to regeneration that may promote transitions in hair growth phases. Photobiomodulation may stimulate cellular activity and prolong growth phases. Contact immunotherapy induces allergic immune responses that promote hair regrowth in alopecia areata, while PRP expedites wound healing and tissue restoration. In androgenetic alopecia, microneedling, lasers, LLLT, and PRP have shown efficacy in increasing hair density and thickness. For alopecia areata, contact immunotherapy, and combination therapies involving microneedling and lasers have demonstrated positive outcomes. Limited studies on telogen effluvium suggest that microneedling and PRP can improve hair density. Microtrauma-based treatments offer promising strategies for hair regeneration. Continued research is necessary to enhance therapeutic options for non-scarring alopecia.