Sunscreen SPF update
New for 2009: SPF 85
A sunscreen's SPF, or sun protection factor, measures how much the product shields the sun's shorter-wave ultraviolet B rays, known as UVB radiation, which can cause sunburn. It used to be that SPF topped out at 30. No more. These days, a race is on among sunscreen makers to create the highest SPF that R&D can buy.If adequately applied, sunscreens with sky-high SPFs offer slightly better protection against lobster-red burns than an SPF 30. But they don't necessarily offer stellar protection against the more deeply penetrating ultraviolet A radiation, or so-called aging rays.
The difference in UVB protection between an SPF 100 and SPF 50 is marginal. Far from offering double the blockage, SPF 100 blocks 99 percent of UVB rays, while SPF 50 blocks 98 percent. (SPF 30, that old-timer, holds its own, deflecting 96.7 percent).
A sunscreen's SPF number is calculated by comparing the time needed for a person to burn unprotected with how long it takes for that person to burn wearing sunscreen. So a person who turns red after 20 minutes of unprotected sun exposure is theoretically protected 15 times longer if they adequately apply SPF 15. Because a lot of sunscreens rub off or don't stay put, dermatologists advise reapplication every two hours or after swimming or sweating.
SKIN DEEP Confused by SPF? Take a Number
By CATHERINE SAINT LOUIS
Published: May 14, 2009
The SPF arms race is leading some dermatologists to complain that this is merely a numbers game that confuses consumers.
Previously:
Mexoryl ingredient in sunscreen protects against UVA, UVB, recommended by
Manhattan dermatologist Dr. Patricia Wexler
And use lots of sunscreen:
"It turns out that if you apply half the amount, you get the protection of only the square root of the SPF," said Dr. Darrell S. Rigel, a clinical professor of dermatology at New York University, who has done efficacy testing for Johnson & Johnson and the Procter & Gamble Company.