What to Look For

Skin cancer is the most common of all cancers in the U.S., and as many as one million people are diagnosed with it every year. Despite these high numbers, skin cancer is preventable with proper protection.

The following are basic criteria when choosing sunscreen:

Mineral Ingredients

Titanium dioxide and zinc oxide are minerals that physically block ultraviolet (UV) rays from reaching your skin, as opposed to other sunscreens that use chemicals to absorb UV rays. Minerals are considered the best protection against sunburn because they block both UVB rays (which cause sunburns) and UVA rays (which cause skin aging and cancer). Chemical sunscreens, on the other hand, don't always protect against UVA. And some break down in sunlight in as little as half an hour, while also interfering with your hormonal systems.

Protection Rating

SPF (or sun protection factor) is an FDA-regulated rating system that represents how long it will take for exposed skin to burn with the sunscreen applied. However, SPF only rates UVB rays, not skin damaging UVA rays. For that reason, never rely entirely on a sunscreen's SPF, and look for products that advertise "broad-spectrum protection," which means it protects against both types of rays.

Nano-sized or Micronized Particles?

A 2006 Australian government literature review found that neither titanium dioxide nor zinc oxide nano-sized particles penetrate the skin deep enough to actually enter the bloodstream, and most scientific evidence supports the fact that nanoparticles of these ingredients are often trapped in the outer layer of the skin and not absorbed (they should always be avoided when used in powders that may be inhaled). However, if you'd rather err on the side of safety, opt for sunscreens that use micronized ingredients (particles larger than 100 nm), which are mostly transparent but may still offer a slight tint.

Shopping Tips

• If you're swimming in the ocean, choose sunscreens with plant-based ingredients to avoid damaging coral.

Usage Tips

• Apply sunscreen generously to exposed skin at least 30 minutes before going out into the sun, and use 1 ounce (enough to fill a shot glass).

• The Skin Cancer Foundation recommends reapplying sunscreen every two hours.

• "Waterproof" and "water resistant" claims aren't regulated and are often inaccurate. Always reapply lotions after getting out of the water, toweling off or sweating heavily.

• Avoid using sunscreens on children younger than 6 months, unless there is no other way to protect them. Keep them out of the sun, instead, to prevent burns and overheating.