Question: What is SPF? How effective is the SPF number on the skin?
Answer: Skin damage from sunlight builds up with continued exposure, whether sunburn occurs or not. In addition to skin cancer and sunburn, other effects can include wrinkling, premature aging, and in time, an almost leathery appearance of the skin. Research also suggests that excessive exposure to UV radiation may interfere with the body’s immune system. If you’ve shopped for sunscreen lately, you have probably noticed the proliferation of products with ever-higher sun protection factor (SPF) ratings.
The sun protection factor of a sunscreen is a laboratory measure of the effectiveness of sunscreen — the higher the SPF, the more protection a sunscreen offers against UV-B (the ultraviolet radiation that causes sunburn)
SPF numbers start at 2 and have just recently reached 70. To figure out how long you can stay in the sun with a given SPF, use this equation:
Minutes to burn without sunscreen x SPF number = maximum sun exposure time
For example, if you burn after 10 minutes of sun exposure, an SPF of 15 will allow you to be in the sun for up to 150 minutes without burning.
Anyone over the age of six months should use a sunscreen daily. Even those who work inside are exposed to ultraviolet radiation for brief periods throughout the day, especially if they work near windows, which generally filter out UVB but not UVA rays.
Sunscreens with higher SPF ratings block slightly more UVB rays, but none offers 100% protection.
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