Quiz: The Burning Facts About Sunscreen

All sunscreens help prevent sunburn, but only some may help lower the risk of skin cancer.  Only "broad-spectrum" sunscreens with an SPF of 15 or higher can claim to lower the risk of early skin aging. Broad-spectrum sunscreens protect your skin from both kinds of harmful rays -- ultraviolet A (UVA) and ultraviolet B (UVB). 

The FDA requires that sunscreens keep their strength for at least 3 years. But if you're using sunscreen every day and in the right amount, a bottle shouldn't last anywhere near that long. Throw it out if it's past the date on the bottle or if the color or feel of the sunscreen has changed.

That's about an ounce. Most people skimp. They only apply a quarter to a half of the amount of sunscreen they should. The total you need depends on your body size, but you should coat all exposed skin.

Use sunscreen every day, even when you won't be outside. Apply it 15 minutes before leaving the house. Re-apply about every 2 hours while in the sun. Do it again after swimming or sweating a lot.

After your moisturizer, you should apply sunscreen, then makeup. Some moisturizers and makeup also have SPF sun protection.

If you're using bug spray, apply it last. When sunscreen is put on top of bug spray, both are less effective.

Nearly all top experts and skin-health groups say sunscreen is safe -- and works! Claims that suggest danger are based on iffy science. A major study tracked more than 1,600 adults over 10 years. Those who wore sunscreen every day cut their risk of melanoma in half.

Overcast skies won't protect your skin from skin cancers or early aging. Up to 80% of the sun's rays pass through fog and clouds. Be extra careful around sand, water, snow, or concrete. These amp up the sun's harmful effects. Wear a hat, along with sunscreen.

Dermatologists recommend using a broad spectrum sunscreen with at least SPF 30. That should block 97% of UVB rays. But no matter the SPF number, you should reapply every 2 hours to make sure you're protected.

In 2013, the FDA began testing all sunscreen products for both UVA and UVB protection. If they pass and have both, they're now called "broad spectrum."

Only broad-spectrum sunscreens with an SPF of 15 or higher can claim to reduce skin cancer and early aging. Others can only say they help prevent sunburn.

The words "waterproof," "sweatproof," and "sunblock" are no longer allowed because they're untrue.

No sunscreen is waterproof. Like all sunscreens, water-resistant products should be reapplied after 2 hours. That's true whether you're in or out of the water. Be sure to reapply after you dry off.

Everyone needs sunscreen. In all races, basal cell carcinoma -- the most common skin cancer -- is usually due to sun exposure.