Sunscreen Tips

April 28, 2009

We know there’s no such thing as a healthy tan, so we dutifully apply sunscreen before we head out. But is there more to it than that? Are we using enough of the right product to ward off premature aging and skin cancer? This summer, protect your youthful looks, maintain your winter pale, and shield yourself from the sun’s unhealthy rays with a quality sunscreen—and the knowledge of how to use it properly.

  The sun unleashes a constant barrage of skin-damaging ultraviolet rays, which are divided into two main types. UVA penetrates deepest into the body; over time it causes wrinkles and premature aging of your skin (“A” is for aging). UVB is what turns you into a seared lobsterback (“B” is for burn). (A third type, UVC, exists as well but is entirely blocked by the atmosphere.) Exposure to UVA and UVB both contribute to an increased risk of skin cancer; more than a mil­lion cases are reported each year in the U.S.

INCOMING!   UV radiation penetrates cloud cover (up to 80 percent makes it through) and is also reflected upward by water (up to 20 percent), sand (15 percent), and snow (80 percent). Glass blocks UVB but not UVA, which means you won’t get a sunburn while sitting in your car but will still be absorbing skin-aging sunbeams. The atmosphere, especially the ozone layer, blocks a significant amount of UV before it reaches the ground. Consequently, UV exposure is greater when the sun is higher in the sky and its rays pass more directly through the atmosphere; the hours between 10 a.m and 4 p.m. provide the maximum dose. For the same reasons, exposure increases at higher altitudes where the atmosphere is thinner—UV levels increase by about 10 percent for every 3,000 feet of elevation gain.

SOME PROTECTION FACTOR   A sunscreen’s efficacy is measured by its SPF, or sun protection factor, an indication of how much UV is being blocked. For example, an SPF of 15 means that it will take 15 times longer to absorb the same amount of UV than if you applied none at all. However, SPF indicates only a sunscreen’s protection from UVB, not UVA, for which there is no equivalent standard. In the fall of 2007, the FDA proposed a one- to four-star labeling system for UVA protection—watch for it in the years ahead. Until then, look for sunscreens that feature “broad spectrum” protection, the only available indication that it blocks UVA to some extent. Keep in mind that sunscreen is guaranteed to keep its SPF rating for only a two-year shelf life, the minimum standard set by the FDA, so toss out that stuff you found buried with the beach towels from 10 years ago. Also note that the DEET found in most insect repellents reduces SPF significantly. If you’re in sun-and-bug country, opt for a higher SPF or wear long pants and sleeves.

SMEAR CAMPAIGN   The most common mistake is not applying enough sunscreen in the first place. The recom­mended amount—and the only way to achieve full SPF protection—is about one ounce for your entire body, or a full palm-load of lotion. It takes approximately 30 minutes for your skin to absorb sunscreen, which means you should apply it before you set foot outdoors or begin activities that can cause it to rub off. Don’t neglect your lips (if you’ve ever experienced the discomfort of swol­len, sunburned lips, you probably won’t); use an SPF-rated lip balm to protect them. Also remember to apply sunscreen to the underside of your nose if you’re spending a lot of time on snow or water. Finally, realize that there’s a slight delay between the time your skin burns and when it turns red. If you notice your skin turning pink, it’s already too late—get out of the sun.

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Matt Heid

Equipped blogger Matt Heid is AMC's gear guru: He loves gear and he loves using it in the field. While researching several guidebooks, including AMC's Best Backpacking in New England, he has hiked thousands of miles across New England, California, and Alaska, among other wilderness destinations. He also cycles, climbs, and surfs.