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On Sunscreen: 4 Common Questions About SPF

Tuesday, June 7, 2011

Pretty much all I knew about sunscreen growing up was that SPF was some measure of how much sunburn protection came out of the bottle. Hard to believe that back in the day, the great debate was "6 or 8," not 30 or 50. (or 110!) We even busted out the baby oil on occasion (oh, the teen years!).

In case you, too, wonder exactly what "Sun Protection Factor" actually is, or how much you need, or whether it's even a meaningful measure - and of what, these four questions are for you:

1. What does "SPF" really mean? Sun Protection Factor is a measurement of protection from sunburn, which is primarily caused by the sun's ultraviolet-B rays. If your skin would normally burn after 30 minutes in the sun, for example, an SPF 15 sunscreen would theoretically let you stay in the sun for 450 minutes without burning (15 SPF x 30 minutes). That's a rough estimate that assumes you apply lots of sunscreen - which most of us don't.

2. What's so bad about high SPF? The more protection the better, right? Not necessarily. The calculations for SPF 15 would lead you to believe that SPF 100 would allow beachgoers to bare their skin to sunshine a hundred times longer before burning. But for high-SPF sunscreens, theory and reality are two different things.

False sense of security. In the real world, people get far less protection than the bottle advertises. Why? Because people typically apply between a fifth and a half of the sunscreen that laboratory tests use to calculate the product's SPF. If you're as stingy with your sunscreen as most people, your 100 SPF sunscreen may have a real world protection factor below 10. One in six sunscreens claim SPFs of 50+. The federal Food and Drug Administration calls those claims "inherently misleading." It doubts current testing methods work for high SPF sunscreens. More sun means more UVA damage, and higher SPF often means more time in the sun. Higher SPF products do effectively suppress sunburn (from UVB rays), but do not fully protect skin from other types of sun damage. The sun's ultraviolet-A (UVA) rays are more common and more penetrating. They don't burn skin (so you can't SEE the damage), but are linked to immune system suppression and the most deadly form of skin cancer, melanoma.

In Europe, UVA protection has to be at least 1/3rd as strong as the SPF rating of the sunscreen. In the US, there are no requirements to "balance" UVB and UVA protection, and many US products offer inadequate UVA blocking relative to the SPF. You need both to adequately protect your skin.

This problem is especially notable for high SPF products. Studies show that users of high-SPF sunscreens stay in the sun longer than people wearing lower SPFs, because they don't SEE that burn and run for cover. Instead, they extend their time in the sun, and more time in the sun means more damaging UVA exposure. The net result is more skin damage for high SPF users than folks who pick a lower SPF product that offers more "balance" between UVA and UVB sun protection.

Increased exposure to potentially hazardous ingredients. High-SPF products contain a greater volume of sun-blocking chemicals than low-SPF sunscreens.

3. What SPF should I use? Pick the SPF appropriate for your skin type (higher for fairer skin) and the solar exposure you'll face that day (full sun? high altitude? July or September?). But remember not to depend on sunscreen as your first line of defense against the sun. Hats, sunglasses, umbrellas and a shirt can offer more complete protection.

The American Cancer Society recommends that people use a sunscreen with a SPF of at least 15 and the American Academy of Dermatology opts for 30. EWG recommends that you avoid sunscreens with SPF numbers higher than 50. A better choice is to use EWG's database to pick a product with very good UVA protection in relation to the SPF -- and always apply a thick coat.

4. I use sunscreen with SPF 50. Why do I still get burned in the sun? Maybe you're not using it correctly. Many of us fall short in the way we use sunscreen - even if we've picked an effective product. To use it right, you should apply sunscreen 20 to 30 minutes before solar exposure, use about an ounce for your entire body (which is more than you think!), and reapply frequently - every 2 hours and after swimming, sweating or toweling off.

Learn more about the problem with high SPFs - and find a safer, skin-protecting sunscreen in EWG's 2011 sunscreen database now. It is June, after all - might as well start the summer off right.

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