Sunlight in Dermatology: Effects, Benefits, and Personalized Photo Protection

Conclusions

• Sunlight has well-established harms for the skin, including pigmentation changes, photoaging, immunosuppression, and photocarcinogenesis, but its effects depend strongly on wavelength, skin type, and dose.
• Visible light, especially blue light, is no longer considered biologically inert because it can cause persistent pigmentation in darker skin through Opsin-3–mediated signaling and suppression of melanosome degradation.
• Visible light and UVA1 can act synergistically to intensify and prolong pigmentary changes, so protection against both wavelengths is important, especially for patients prone to hyperpigmentation.
• Sunlight also appears to have systemic benefits, influencing circadian rhythm, mood, immune function, cardiovascular health, and metabolic regulation, although the strength of evidence varies and many studies have important limitations.
• Lower sunlight exposure is associated in multiple observational studies with worse outcomes such as more respiratory infections, more COVID-19 cases, higher blood pressure, more metabolic risk, and higher all-cause mortality.
• A likely mechanism for some of the systemic benefits of sunlight is nitric oxide release from the skin, which may help lower blood pressure and improve vascular function independently of vitamin D.
• Vitamin D is only one piece of the sunlight-health relationship, and several beneficial effects of sun exposure may occur through non–vitamin D pathways.
• Because both benefits and harms exist, the best public-health message is not total avoidance or unrestricted exposure but a balanced, individualized approach to sun exposure.
• Photoprotection should be personalized by skin type and risk profile, with lighter skin generally needing stronger UVB protection and darker skin needing particular attention to visible-light pigmentation.
• Tinted sunscreens containing iron oxides are currently the best practical option for visible-light protection, while newer broad-spectrum filters may improve coverage of long-wave UVA and visible light.
• Biological photoprotection with non-filtering topical ingredients such as antioxidants, nicotinamide, thiamidol, photolyase, and melasyl may add benefit, but the evidence base is still limited for many products.
• Overall, the presentation argues that clinicians should educate patients with nuanced, evidence-based advice that balances the known harms of sunlight with its potential health benefits.