SPF What? A Primer On Selecting a Sunscreen

Pick a sunscreen any sunscreen.

The options for what to slather on before going to the beach are proliferating beyond the oils, lotions, creams, gels, and sticks. Now there's sweat-proof sunscreen. The waterproof stuff. The bug and sunscreen for kids - and a different dosage for adults. A dizzying palette of sun-block colors and a numerical SPF code that isn't what it seems.

If you're confused, here's a primer on making your way through the world of commercial sun protection.

Blocks and screens. There are two types of sun protectants - blocks and screens. While blocks deflect the sun away from your skin, sunscreens chemically absorb ultraviolet rays.

UVA rays are the sun's penetrating rays, which pass through window glass, while UVB rays are the sun's tanning rays. Neither the block nor the screen is necessarily better, say experts.

Deciphering the SPF code. Whether selecting block or screen, you should choose one with a sun protection factor (SPF) of 15 or higher - that gives about15 times the skin's normal protection, says Harold Milstein, co-director of the Dermatological Center based in Philadelphia.

At the high end of the SPF code, bigger does not necessarily mean better. Factors 30 and above are only a fraction more protective than those between 15 and 30. "A factor 15 blocks out 93 percent of all UV rays, while a factor of 30 blocks out about 97 percent of them," says David Lefell, a dermatology professor at Yale University in New Haven, Conn.

Higher SPF lotions may not be worth the extra cost because they rub off or wash off as frequently as lower numbers. You use just as much sunblock, but pay more for it. "There's not enough benefit to pay for the difference in price," says Dr. Milstein.

Waterproofing. To cater to the play habits of children - frequent dips, in and out of the water - products such as Jungle Land, and Waterbabies offer waterproof lotions.

Waterproof sunblocks stay on the longest because they can withstand everything from water to friction and rubbing. For the beach volleyball crowd, there are now sports sunblocks like Active! that are sweat-proof. But even the most enduring of applications won't last more than 80 minutes.

Body art on the beach. For added pizazz, try brands like Coppertone Kids Colorblock, which come in bright colors like purple and green. Don't worry, the Wild Man of Borneo look fades after application. No color is better than another, in terms of sun protection. But the coloring does help prevent missing spots as you apply it.

Bug and sun protection. The insect repellent-sunscreen combination gives "total outdoor protection." It may be more convenient but experts advise that you separate bug spray and sunscreen. "You need to keep re-applying sunscreen more often than the bug repellent, and there's no point in adding extra DEET [the chemical N,-N-diethyl-m-toluamine] to your skin for no reason," says Dr. Milstein.

Experts also warn that for children, it's not a good idea to keep re-applying sunscreen that contains 10 percent DEET or more. Use a separate repellent for children or buy non-DEET sunscreen/bug repellent combinations containing soybean or citronella oil.