Health Team

Using Sunscreen Involves 2 Critical Steps

Posted June 27, 2007 10:36 p.m. EDT

Skin cancer represents more than half of all cancer cases in the U.S. every year.

While many people make sunscreen lotions and sprays a habit when they're outdoors, they only protect your skin when you follow the directions.

The two critical steps in using sunscreen is the amount and how often you reapply it. Some studies show most people only apply 25 to 50 percent of the recommended amount of lotion. Tests that determine the sunscreen's SPF or "sun protection factor" are based on that recommended amount.

The average adult body needs about three tablespoons of sunscreen. And it takes the skin 15 to 20 minutes to absorb the lotion, so don't wait until you're out in the sun to apply it.

The other problem is how long the sunscreen is effective. Most sunscreens need reapplying after two hours. Now waterproof or sweat proof sunscreen are big factors to consider as well. If the sunscreen isn't water or sweat proof, it may need to be reapplied more often.

Some newer products offer longer recommended time between reapplication of the lotion. Some products contain Helioplex. Parsol is the ingredient in some products that blocks the ultra violet waves that burn.

UNC dermatologist Dr. Nancy Thomas says Helioplex makes the Parsol work longer so that you can reapply it every four hours instead of two. But again, you need to follow the directions on the amount you use to make it effective.

Sunscreen is important, but many people wisely reduce their risk of sunburn and skin cancer with sun protective clothing and broad brimmed hats. It gives them fewer areas of the body to cover with sunscreen.