It is the ultraviolet light present in sunlight that causes tanning, burning and damage. The ultraviolet spectrum is arbitrarily divided into the UVA and UVB portions. In general, the UVB rays mainly cause sunburns. The UVA rays are more dangerous and can cause genetic damage to the skin that leads to skin cancer, including melanoma, and premature aging of the skin. If you don't want wrinkles, you need to avoid UVA exposure. Most sunscreen products are effective at blocking UVB but most do not offer adequate protection against UVA. Because blocking UVB means you can stay out in the sun all day without burning, choosing the wrong sunscreen may unwittingly increase your exposure to UVA and do more damage than if you had quickly burned and gotten out of the sun.