Biological Photoprotection: A Review of its Mechanisms, Evidence, and Clinical Implications.

Biological photoprotection refers to the enhancement, preservation, or mimicry of the skin's intrinsic defense systems to prevent or mitigate damage induced by solar and environmental stressors. Unlike conventional sunscreens, which primarily act by reducing photon penetration, biological photoprotection targets the downstream molecular and cellular responses triggered by these exposures. It is achieved by incorporating nonfiltering photoprotective ingredients (PINGs) into sunscreens, which act on key biological pathways involved in skin damage and recovery. Emerging evidence suggests that these ingredients may provide additive protection when combined with ultraviolet (UV) filters, particularly in mitigating oxidative damage, supporting DNA repair, and modulating inflammatory and pigmentary responses. However, the current evidence base remains limited, with many studies characterized by small sample sizes, short durations, and heterogeneous methodologies. Taken together, biological photoprotection represents a complementary, but still evolving, dimension of modern photoprotection. Further research is required to establish standardized evaluation methods and to determine its clinical relevance under real-world conditions.