People who plan to spend time outdoors this summer should take note of a study on sunscreen use quietly released last season. "Mechanisms of Sunscreen Failure"* reported on a survey of Texas beachgoers and found that 73% of those who used sunscreen got a sunburn anyway.

Too much sun exposure to poorly protected skin is the main cause of skin cancer, including melanoma, the most serious form of skin cancer.

Many people didn't use enough sunscreen, or they didn't reapply it as often as they should have, wrote co-author Richard F. Wagner, MD, Professor of Dermatology, University of Texas Medical Branch at Galveston. Study participants were asked about sunscreen use at a Galveston, Texas beach on a Fourth of July.

"A common misconception about sunscreen is that just because you apply it once, you’re covered," said Dr. Wagner.

Many people mistakenly thought their sunscreen would protect them for three to four hours. But dermatologists say it needs to be reapplied after two hours and immediately after swimming or vigorous activity.

And a light coat won't do, according to Mary O'Connell, who directs the Society's Skin Cancer Initiatives. "You have to use pretty generous amounts to get the protection. If you spread it thinly, the effect is only half of the SPF factor listed on the bottle."

Health experts are still trying to get the word out that sunscreen is only one small part of the plan to save your skin. ACS also recommends hats, tightly-woven clothing, and shade. "People should not use sunscreen to extend their time in the sun," says O'Connell.

"Use the methods in combination. If you're sitting out in your bathing suit, put on a shirt after a while," O'Connell added.

People of all skin tones can get skin cancer and should know their personal risk factors for the disease. Fair-haired people have a higher risk for sunburns and cancer. But African Americans can develop skin cancer too, particularly on the palms, feet and under the nails.

ACS Quick Tips for Using Sunscreen Correctly

- Use SPF15 or higher on all skin exposed to the sun.
- You'll need at least one ounce to cover your body effectively.
- Reapply every two hours and after swimming, sweating, or toweling dry.
- Use sunscreen even on hazy or partly-cloudy days.
- Put it on 15-20 minutes before going out in the sun.

The Texas beachgoers who did not go home with a painful sunburn all reapplied sunscreen every one to two hours and right after going swimming.

The Texas study also painted a revealing picture of who's using sunscreen and who's not:

- 78% of the women interviewed used sunscreen
- 34% of the men interviewed used sunscreen
- 69% of women covered all exposed skin with sunscreen
- 14% of men covered all exposed skin with sunscreen

Cancer researchers have noted that men are more likely to develop non-melanoma skin cancers than women, but sunscreen use may not be the only factor.

More than one million Americans will develop the highly curable basal cell or squamous cell skin cancer this year. And about 53,600 people are expected to be diagnosed with melanoma, the most serious skin cancer.

The vast majority of skin cancers are caused by too much ultraviolet radiation exposure (a part of sunlight). And weekend or holiday sunburns, like those seen at Galveston beach on the Fourth of July, can be especially harmful.

Researchers say those intense, occasional exposures to UV rays are more closely linked to melanoma later in life than shorter everyday exposures to sunlight. Even if the total amount of UV exposure is the same, the weekend sunbather will have a greater risk of developing melanoma.