Aug 22, 2008 (The Eagle-Tribune – McClatchy-Tribune News Service via COMTEX)
According to the American Academy of Dermatology, an SPF of 15 or higher should be enough to protect most people when they are out in the sun. However, SPF is an imperfect indicator of protection against UV radiation.
In the United States, the FDA tests sunscreen on certain individuals in an “in vivo” test. It’s imperfect, because the amount of melanin in individual skin differs, and therefore the amount of sun exposure it takes for a person to burn varies.
Additionally, many sunscreens protect only against UV-B radiation, the kind of rays that cause visible burns and redness. UV-A rays are invisible, but they do cause wrinkles associated with aging.
To be sure you are protected from both kinds of rays, look for bottles of sunscreen that say they have a “broad spectrum coverage,” the FDA advises. Under U.S. law, only sunscreens that protect against both kinds of rays can carry such a label.