Blue light and ultraviolet radiation: comparative biophysical properties and their roles in skin carcinogenesis and photoaging

Ultraviolet radiation (UVR), especially UVB and UVA, drives photoaging and carcinogenesis, whereas blue light (BL, 400-500 nm) remains less studied. Evidence shows BL induces melanogenesis, generates reactive oxygen species, impairs deoxyribonucleic acid (DNA) repair, and accelerates pigmentation and oxidative stress. Though not directly linked to skin cancer, BL amplifies UVR damage and hastens photoaging, yet also suppresses tumor growth by promoting apoptosis, revealing dual context-dependent effects. This review highlights BL's biological and clinical relevance, phototype-dependent responses, and mechanistic uncertainties. Expanding photoprotection beyond UVR to include BL is essential for comprehensive, evidence-based strategies safeguarding skin health across diverse populations.