Ultraviolet Radiations Impact on the Skin-Brain Axis: A Literature Review of our Current Knowledge

Sunlight is essential for vitamin D synthesis and contributes to mood regulation, but it is also a major risk factor for skin aging and carcinogenesis. While the cutaneous and immune effects of ultraviolet radiation are well documented, its potential impact on brain function remains poorly understood. This review aims to synthesize current evidence on the effects of ultraviolet exposure on the central nervous system, with a particular focus on photoimmunological mechanisms and skin-derived signaling pathways.

We conducted a narrative review of experimental and clinical studies investigating the systemic and neurological consequences of UV exposure. Findings from photodermatology, immunology, neuroscience, and microbiome research were integrated to examine potential skin-brain interactions.

UV exposure induces systemic inflammatory responses and immunosuppression, alters the skin microbiome, and modulates circulating neuroactive mediators. These processes are associated with changes in neurotransmitter systems, neuroplasticity, and brain structure in both animal models and human studies. Emerging evidence supports the existence of indirect pathways linking UV-induced skin and immune responses to central nervous system function, including immune and microbiota-related mechanisms.

Collectively, available data suggest that UV radiation may influence brain function indirectly through interconnected skin, immune, and microbiota pathways. As interest in balanced and "healthy" sun exposure increases, further interdisciplinary research is needed to clarify the neurological consequences of UV exposure and to assess its potential implications in photodermatology and photomedicine.