Sunscreen protects your skin from the sun's ultraviolet, or UV, rays. Two types of UV rays, known as UVA and UVB, trigger harmful changes in your skin. ... The Skin Cancer Foundation recommends that everyone -- regardless of skin color -- protect their skin by wearing sunscreen.
Protection from sunburn is not the most important reason for wearing sunscreen. You want to reduce damage from the sun. Your skin can be harmed by constant sun exposure, whether or not you see a burn. Remember, sunburn is an immediate reaction, but damage from the sun occurs over a lifetime.
Sunscreens should be applied 30 minutes before sun exposure to allow the ingredients to fully bind to the skin. Reapplication of sunscreen is just as important as putting it on in the first place, so reapply the same amount every two hours