Do you know what the SPF number on your sunscreen really means? The SPF (or Sun Protection Factor) is the ratio of the amount of time it takes for your skin to turn red in the sun with sunscreen on, as compared to the time it takes for your skin to turn red without sunscreen. So, if your skin would normally start to turn red after 10 minutes in the sun without sunscreen, then applying sunscreen with an SPF 15 would allow you to stay in the sun for 15 times longer, or 150 minutes, before your skin would turn the same color. A good sunscreen will help protect against UVA and UVB rays.
Children and teens are more sensitive to sun exposure than adults because their outermost layer of skin is thinner. So make sure you layer it on before you go outside!
For more facts about sun exposure and sunscreen, check out our Science in Context database. Search for "Sunscreen."
("Sunscreen." World of Invention. Gale, 2006. Gale Science In Context. Web. 16 June 2012.)