UV Radiation and Photoaging

Photoaging is the cumulative skin damage from chronic exposure to the sun's ultraviolet (UV) light. It is distinct from intrinsic aging (chronoaging). UVA (320 to 400 nm) reaches deep into the dermis. There, it generates reactive oxygen species. It also switches on enzymes called matrix metalloproteinases (especially MMP-1, MMP-3, MMP-9). Those break down your collagen and elastin. The result is wrinkles, sagging, and a leathery look (solar elastosis). UVB (280 to 320 nm) is absorbed in the upper skin (epidermis). There, it forms specific DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts). If those go unrepaired, they drive non-melanoma skin cancer. Even a single moderate UVB dose suppresses new collagen for about 24 hours. Your skin-aging 'exposome' goes beyond UV, too. It also includes infrared-A, visible light, particulate air pollution, and tobacco smoke. One thing has consistent evidence for slowing measurable photoaging: daily broad-spectrum sun protection (SPF 30+, UVA-PF ≥ 10).

Last reviewed: June 22, 2026

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