Don't Ignore These Facts About Sunscreen

The sun's power is undeniable: The largest object in our solar system, it contains approximately 99.9 percent of the total solar system mass. Its interior could hold more than 1.3 million Earths. The sun provides for our very life. But this 4.5 billion-year-old star also has the power to kill.

Melanoma, the most dangerous and potentially lethal form of skin cancer, is caused most often by intense UV rays of the sun, and its rates have been rising for at least 30 years. About 73,870 new melanomas will be diagnosed in the U.S in 2015, and approximately 9,940 people are expected to die, according to the American Cancer Society.

The typical victim? On average, a person is 62 when the cancer appears. The risk of melanoma increases as we age.

The other two types of skin cancers, squamous cell carcinoma and basal cell carcinoma, though usually not life-threatening, must be taken seriously, too, cautions Skin Cancer Foundation spokesman Dr. Lindsay Sewell, a dermatologist based in Idaho Falls, Idaho.

"The sun's UV rays play a crucial role in skin cancer development," he says. "About 86 percent of melanoma cases and about 90 percent of non-melanoma skin cancers can be attributed to ultraviolet (UV) radiation from the sun."

That's one reason why it's so vital to use sunscreen — which can be a formidable foe against the sun's powerful UV rays. Those rays are so powerful that they've been called "a human carcinogen" by the National Institutes of Health and the World Health Organization.

For those of you who think the damage was already done when you were a child, think again: The Skin Cancer Foundation reports a recent study showing that we get less than 25 percent of our total sun exposure by the age of 18. So it's never too late to make sunscreen a daily habit.

Sunscreens help prevent two types of ultraviolet radiation from reaching your skin.

One type, UVA rays, (present all-year-round), ages your skin prematurely (think of the A in UVA for 'Aging'). These rays penetrate more deeply and cause wrinkles, sagging and other light-induced effects of aging. The other, UVB rays (whose intensity varies by season, time of day and location), are the ones responsible for sunburn (think of the B in UVB for "Burning'). Both types of rays can lead to skin cancer.

SPF, which stands for sun protection factor, is a measure of the sunscreen's ability to prevent UVB rays from damaging your skin.

Although it had been thought an SPF of 15, for example, meant that you can stay in the sun 15 times longer than it would take your unprotected skin to start turning red, that theory is no longer a reliable measure, says the Skin Cancer Foundation. They say that no sunscreen — regardless of its strength — can be expected to protect anyone longer than two hours and that reapplication is necessary.

The American Academy of Dermatology recommends that everyone use a water-resistant, broad-spectrum sunscreen (this protects against both UVA and UVB rays) with an SPF of 30 or higher, which blocks 97 percent of the sun's rays. But a higher SPF does not mean you can stay out longer without re-applying it. High-number SPFs last the same amount of time as low-number SPFs, dermatologists say.

Granted, it can get confusing, since many of the sunscreens on the shelves combine several different ingredients.

"The blockers are the best, like titanium dioxide and zinc oxide," notes board-certified dermatologist Dr. Jennifer Reichel. "They make some great formulations now with tints and micronized particles that keep them from looking white on your skin."

Landmark research out of Australia has found strong evidence that the use of a daily application of broad-spectrum sunscreen to the head, neck, arms and hands can reduce the incidence of melanoma by half.

But if you're not applying it correctly, all bets might be off. Five tips:

1. Apply it in the nude. No, we're not suggesting stripping down on the beach to slather on the sunscreen. Rather, put it on before you even get dressed to go out in your swimwear or clothing and about 20 to 30 minutes before you venture out, suggests Reichel. This way, you'll be less likely to miss certain spots and end up with an unexpected burn, like along the outer edges of your bathing suit (ouch!).

2. Check expiration dates. Although the FDA requires all sunscreens to retain their original strength for at least three years, not every bottle is marked with an expiration date. To prevent guessing games, write the date you purchased your sunscreen on the bottle with a permanent marker, so there will be no question when to throw it out. Also, be on the lookout for any visible signs that the product may no longer be good, like changes in color or consistency.

3. Use enough. Studies show that most of us use only 25 to 50 percent of the recommended amount of sunscreen (which means that we're not getting the full SPF benefits), according to the Skin Cancer Foundation.

Most dermatologists recommend one ounce — which is enough to fill a shot glass (or two tablespoons) — but that amount should be adjusted depending on your body size, of course. If you plan to spend a day at the beach, you should figure on using up to one-half to one-quarter of an 8-ounce bottle.

4. Reapply often. Sunscreen does wear off, even if it's labeled "sweatproof" or "water resistant." Although current FDA guidelines are for a water resistant product to maintain its SPF after 40 minutes of water immersion and a "very water resistant" product to be effective for up to 80 minutes, the Skin Cancer Foundation says that all sunscreen should be reapplied every two hours or immediately after swimming, toweling off or heavy sweating.

5. Don't forget the lips and tops of your feet. It's possible for skin cancers to develop on your lips, so protect your lips by using a balm or lipstick containing an SPF of 30 or higher. And on the other end of your body, don't forget the tops of your feet, another vulnerable – and tender – body part.