Which type of UV rays are known for causing aging and penetrate the reticular dermis?

UVA rays are responsible for causing premature skin aging, also known as photoaging. They penetrate deeper into the skin than UVB and UVC rays, reaching the reticular dermis. This layer of the skin contains collagen and elastin fibers, which are essential for maintaining skin's firmness and elasticity. The damaging effects of UVA rays include the breakdown of collagen, leading to wrinkles, fine lines, and loss of skin elasticity.

In contrast, UVB rays primarily affect the epidermis, causing sunburn and contributing to the risk of skin cancer; they do not penetrate as deeply as UVA rays. UVC rays are largely absorbed by the Earth's atmosphere and do not typically pose a threat to skin. Infrared rays, while they can contribute to heat and have some effects on skin, are not primarily associated with aging in the same way UVA rays are. Understanding the roles of these different types of UV rays highlights the importance of broad-spectrum sun protection to mitigate skin damage and aging.