What type of rays are primarily responsible for skin aging and tanning effects?

UVA rays are primarily responsible for skin aging and tanning effects due to their ability to penetrate deep into the skin layers. These rays can cause changes in the structure of skin proteins, leading to premature aging signs such as wrinkles and loss of elasticity. UVA rays are present throughout the day, regardless of the season, and can penetrate glass, making them a continuous threat to skin health. This is why sunscreen that offers broad-spectrum protection is essential; it should protect against both UVA and UVB rays. UVB rays, while they do contribute to tanning and the risk of sunburn, primarily affect the outer layer of the skin and are more associated with the immediate effects of sun exposure rather than long-term aging. Infrared rays and visible light, though capable of affecting the skin, do not play the same significant role in aging and tanning as UVA rays do.