How to select a sunscreen:
Select a water-resistant, broad-spectrum sunscreen with a SPF of 30 or higher.
SPF stands for Sun Protection Factor. The higher the SPF, the more protection from ultraviolet B (UVB) rays, which prevents sunburn. But SPF does not tell you about the level of ultraviolet A (UVA) protection.
A broad-spectrum sunscreen protects against both ultraviolet A (UVA) and ultraviolet B (UVB) rays to all exposed skin. Both UVA and UVB increase your risk of skin cancer and cause skin aging. The best broad-spectrum sunscreens have the following 2 active ingredients: avobenzone and octocrylene (look for them on the list of active ingredients on back of bottle).
How to use a sunscreen:
Generously apply sunscreen to exposed skin EVERY DAY, 30 minutes PRIOR to going outdoors. Re-apply the sunscreen every 2 hours even on cloudy days or after swimming or sweating heavily.
You should be using one ounce, enough to fill a shot glass, each time, in order to cover typical exposed skin, including your face, neck, chest, and arms.