Which UV rays primarily cause skin aging?

UVA rays are primarily responsible for skin aging. These rays penetrate the skin more deeply compared to UVB rays and are a major contributor to photoaging, which includes the appearance of wrinkles, fine lines, and loss of skin elasticity. UVA rays can also cause damage to collagen and elastin, essential proteins that maintain the skin's structure and firmness.

While UVB rays play a significant role in causing sunburn and contribute to skin cancer risk, they do not penetrate the skin as deeply as UVA rays do, and thus have a less direct impact on skin aging. UVC rays are mostly absorbed by the Earth's atmosphere and do not significantly reach the surface, so they do not have a meaningful effect on skin aging. The term UVD rays is not commonly recognized in the context of UV radiation, as it is not an established classification like UVA, UVB, and UVC.