Biological and Therapeutic Responses of Human Skin to Different Wavelengths of Light: A Comprehensive Review

<b>Introduction:</b> Light-based therapies have emerged as promising, noninvasive approaches in dermatology and regenerative medicine. Different wavelengths within the visible and near-infrared spectrum produce distinct biological effects on skin tissue, influencing pigmentation, inflammation, wound healing, collagen synthesis, and aging. Objective: This review aims to summarize current evidence on cellular and molecular mechanisms underlying skin-specific responses to various wavelengths within the visible and near-infrared spectrum, including violet, blue, green, yellow, red, and near-infrared light. <b>Methods:</b> A comprehensive literature review was conducted, including data from in vitro, in vivo, and clinical studies addressing wavelength-specific biological responses, therapeutic potential, and safety profiles. <b>Results:</b> Findings suggest that violet light and blue light display antimicrobial and anti-keloid activity but may also induce oxidative stress. Green light and yellow light mainly support wound healing, angiogenesis, and collagen preservation. Red light and near-infrared light are well established for photobiomodulation, skin rejuvenation, and wound repair, though optimal dosing and long-term safety require further study. Safety concerns such as oxidative stress, DNA damage, and pigmentation, especially in darker skin phototypes, are highlighted. <b>Conclusion:</b> Light-based therapies hold significant promise for dermatological and aesthetic applications. Nonetheless, standardized treatment protocols and randomized clinical trials are essential to determine optimal wavelength parameters, dosing strategies, and long-term safety.