Skin cancer is the most common form of cancer in the United States. More than 1 million cases are diagnosed annually, according to the National Cancer Institute. One in five Americans and one in three Caucasians will develop skin cancer in the course of a lifetime.

Melanoma, the deadliest form of skin cancer, is now the second most common cancer in women between the ages of 20 and 29, the American Cancer Society says. It claims an estimated 8,000 lives annually in the United States and will strike 62,000 Americans this year. Meanwhile, the rates of basal-cell carcinoma and squamous-cell carcinoma - the two less-lethal forms of the disease - have more than doubled in the past generation among 20- and 30-somethings, says a 2005 report from the Mayo Clinic.

But not all the statistics are so dismal. More than 90 percent of all skin cancers are preventable, and with early detection, the survival rate for people with skin cancer is about 99 percent. The key to preventing and surviving skin cancer is knowing the facts about the disease and sun damage.

MYTH VS REALITY

Dermatologists clear up some common misinformation and misconceptions about skin cancer and sun protection:

- MYTH: You can prevent skin cancer by putting on one application of sunscreen at the start of beach day.

Using sunscreen daily is a good habit to get into. But smearing it on only after your morning shower can give a false sense of security.

"One application of sunscreen is not good for the day. We sweat it off and it rubs off and we need to reapply it every two to three hours," says Dr. Susan Stuart, a dermatologist at Scripps Memorial Hospital in San Diego, noting that most people need enough sunscreen to fill a 4-ounce glass to cover their body's surface.

But, no matter how much or how well you apply sunscreen, it still only gives a certain amount of protection.

"Even with a high-SPF sunscreen, you still get some sun," says Dr. Curt Littler, a dermatologist with Sharp Rees-Stealy Medical Center in San Diego. "In addition to wearing sunscreen, you also need to avoid the sun as much as possible during midday and wear protective clothing."

- MYTH: Visible symptoms of skin cancer will show up within a year or two of bad sunburns.

The risk of skin cancer is based on accumulative sun damage.

"It's not an overnight phenomenon. You can develop skin cancer 10, 20 or 30 years down the pike," says Stuart, who adds that skin damage such as wrinkling, blotchiness and a leathery appearance can show up weeks or months after the sun exposure.

"More than one bad sunburn in childhood puts you at risk for skin cancer for the rest of your life," says Dr. Richard Gallo, chief of the division of dermatology at University of California San Diego Medical Center.

- MYTH: Getting a base suntan protects you from skin cancer.

The term "healthy tan" is a contradiction in terms. A tan is really a sign of injury to the skin. In an effort to protect itself from further damage, the skin cells produce a pigment called melanin, which darkens the skin. By the time the tan develops, permanent damage has been done and will someday show up in the form of wrinkles, blotches, sagging tissue and even skin cancer.

"There is no such thing as a safe tan. No matter if you're tanning your skin or burning your skin, it's all sun damage," Stuart says.

- MYTH: Tanning salons will not give you skin cancer.

"A tan from a suntanning parlor is the worst kind of tan," says Dr. Mitchel Goldman, dermatologist and assistant professor of dermatology at University of California San Diego. "There have been a number of studies showing that (people who regularly use tanning salons) have a higher rate of malignant melanoma, because the ultraviolet A rays used by tanning salons penetrate deeper into the body."

Several studies have linked indoor tanning to all three skin-cancer types. In 2001, Johns Hopkins University found that just 10 indoor tanning sessions sparked skin changes linked to cancer. Research from the National Cancer Institute in 2002 showed tanning-bed use increased a person's odds of developing squamous-cell carcinoma 1 1/2 times and boosted the risk of basal-cell carcinoma by 50 percent. A 2003 Norwegian and Swedish study showed that one or more indoor tanning sessions a month increased a woman's melanoma risk by 55 percent.

"Tanning salons are a far cry from safe. It's amazing how many of my gorgeous patients go into (tanning) salons like a rotisserie chicken and think they are safe (from skin cancer)," Stuart says, explaining that tanning lights emit both UVA and UVB rays. "The UVA rays (believed to cause premature aging and melanoma) are so concentrated in the tanning beds that you get 10 times more than what you'd get outdoors."

- MYTH: You'll only get skin cancers on areas of the body that receive maximum sun exposure.

While this is generally true for basal-cell and squamous-cell carcinomas, melanoma will show up on areas of the body that get little if any sun, including the soles of the feet, buttocks, vagina and between the toes. Genetics can play a role in where melanoma shows up.

"The skin is an organ like the heart and the kidneys. Skin cells in the legs are linked to the buttocks, which are linked to the skin cells in the ears. Because the skin is linked together, melanoma will show up anywhere on the body," Goldman says.

- MYTH: A white T-shirt worn over a swimsuit protects your skin from the sun.

The typical white T-shirt has an SPF of only 7 and even less when it's wet. You need tightly woven garments and the darker the garment's color, the more protection you'll get from it.

Dermatologists recommend wearing special sun-protective clothing with an equivalent protection factor of an SPF 15 to 30.

- MYTH: SPF 15 sunscreen is adequate for everybody. SPFs higher than that are just marketing ploy.

The sun-protection factor number is the interval of time it takes to burn. If your skin typically starts to burn in 10 minutes without any sunscreen, wearing an SPF 15 would extend that 10-minute burning time 15 times, to 150 minutes.

"What causes skin cancer is cumulative sun exposure over an entire lifetime, so the more UV light you can block out with higher numbered sunscreens, the better you'll be," Littler says. "I recommend high SPF sunscreens of 30 or more to my patients all the time. The difference between an SPF 15 and a 30 can add up over time."

- MYTH: The use of sunscreen leads to vitamin D deficiency.

Sunlight helps make vitamin D in the skin. However, only a few minutes of sunlight a day is necessary for adequate formation of vitamin D. Most scientists agree that alternate sources of vitamin D in fortified foods and supplements are just as effective.

"The risk of sun damage to the skin without sunscreen is so much greater than (the risk of) vitamin D deficiency," Gallo says.

- MYTH: Blacks, Hispanics and other people with darker skin colors don't get skin cancer.

"Nobody from any descent is immune to skin cancer. People with darker skin may have lower risks, but they can still get it," Stuart says.

Darker-skinned people have higher levels of melanin, the natural chemical that gives skin its pigment. Melanin helps repel UV rays, so the more you have naturally, the more protected you are.

But people with darker skin still can get skin cancer, and when they do, it tends to turn up along body areas with less pigment, like the soles of the feet, the palms or under a fingernail or toenail.

- MYTH: Staying submerged in water will protect you from the sun.

Sixty percent to 80 percent of UV radiation is transmitted through the first 12 inches of water in a pool, so staying submerged won't keep your skin safe. Water also reflects 100 percent of UV light, so you're at risk from the additional rays bouncing off the pool or ocean surface and onto your skin.

And don't think that an extra smear of sunscreen will protect you. Most sunscreens are water-resistant, not waterproof, despite what the label says.

- MYTH: It's impossible to repair skin damage caused by the sun.

"The human body is an amazing organism. It is possible to repair and reverse skin damage and prevent the development of skin cancer," Goldman says.

Although consistent sunscreen use and avoiding sun exposure can help, medications like retinoids and some high-tech laser therapies can help repair skin damage. Pre-cancers of the skin can also be treated so they don't develop into cancer.

"The skin is always repairing itself, so just preventing further (sun) damage will give the skin a chance to recover," Gallo says.