Why SPF Matters
SPF (Sun protection factor) measures protection from sunburn caused mainly by UVB rays, but it does not adequately measure how well a sunscreen protects from skin aging and other effects caused primarily by UVA rays. It is a measurement of how long you can stay in the sun with sunscreen before getting burned. Applying sunscreen with an SPF of 15, for example, means that it will take 15 times longer for your skin to begin to burn than it would without sunscreen. However, sunscreens should not be used to increase the time you spend in intense sunlight.
For the best protection, look for the following on sunscreen labels:
--Broad spectrum: provides protection against both UVA and UVB rays
--Water resistant
--Photostable: describes UV protection that won’t break down when exposed to strong UV rays; sunscreens that include helioplex and Purescreen technologies provide long-lasting, photostable protection.