Teen Tanning Habits Raise Skin Cancer Risks
Tanning, Skin Cancer Myths Debunked by Dermatologists
WebMD News Archive
Researchers say sunscreens are the most common form of sun protection, but many people are confused about how to use them correctly. Sunscreen is formulated to boost the body's natural defenses against harmful ultraviolet radiation by absorbing, reflecting, or scattering the sun's rays on the skin.
The sun protection factor (SPF) of a sunscreen is calculated by comparing the amount of time needed to cause sunburn on unprotected skin. For example, a sunscreen with an SPF of 15 would allows someone to extend that burning time by 15, so it would take 15 times longer for the skin to become burned if the product is used correctly.
But the SPF only reflects the product's protection against the burning UVB rays and doesn't say anything about the protection it provides against the aging UVA rays.
"The only way you can tell if a product provides UVA protection is it will be labeled as broad spectrum," says sunscreen expert Zoe Draelos, MD, associate professor of dermatology at Wake Forest University in Winston-Salem, N.C.
The AAD recommends using a broad-spectrum sunscreen with an SPF of at least 15 for basic, year-round protection. A sunscreen with an SPF of 15 provides protection against about 93% of the sun's burning UVB rays.
Draelos says reaching for a higher SPF doesn't necessarily provide significantly more protection and may be much more uncomfortable to wear. To increase the SPF beyond 15, additional active ingredients are needed that often cause the sunscreen to become sticky or pasty, which may make people less likely to use them properly.
"If you go from a 15 to a 30, for the increase in stickiness you only get 4% increase in sun protection, from 93% to 97%," says Draelos. "To go from a 30 to a 45, you've got to add even more of the sticky and pasty sunscreen ingredients, but you only get a 1% increase in the protection against UVB light."
For maximum protection, sunscreen should be applied 15-30 minutes before going outdoors and reapplied every two hours. The active ingredients in sunscreens begin to degrade after two hours and are virtually gone after four hours, says Draelos.
Vitamin D and the Sun
Researchers also addressed recent reports linking the health benefits of vitamin D to unprotected sun exposure. Vitamin D is a vital nutrient that is converted from the inactive to active form in the body with exposure to sunlight.
Dermatologist Darrell Rigel, MD, says normal vitamin D levels are easily obtained through routine daily activities and intentional, unprotected exposure to UV rays does not produce additional health benefits.
He also debunked the myth that sunscreen interferes with vitamin D absorption.
"There is no data to show that low vitamin D levels exist from the use of sunscreen," says Rigel, who is a professor at New York University Medical Center. "There is no such thing as a safe tan."