Diana Warren of Scott City, Mo., makes certain she and her toddler son are lathered in sunscreen before they head to the pool for an afternoon.

Aaron Ulrich applies sunscreen regularly during his shift at Capaha Pool in Cape Girardeau, but some of his co-workers, like Jessica Summary, don't worry much about the harmful effects of the summer sun.

"I like a good tan," said Summary, 17. She rarely applies sunscreen on her arms or legs while sitting poolside. "I'll put it on my nose sometimes because that's where I get pink."

Pink, sunburned skin can lead to more serious health problems, which is why the city provides sunscreen to its lifeguards at Central and Capaha pools.

"It's very important for them to protect their skin," said Doug Gannon, a recreation specialist with the Parks Department who manages the pools.

"They all wear sunscreen, particularly when the summer first starts out," Gannon said of the staff. "They will sit out the first day or two and get burned and I encourage them to introduce themselves very slowly."

Lifeguards with more job experience usually tend to wear more sunscreen because they've gotten burned a few times or are in a position where they are more concerned about the threat of cancer, Gannon said.

The key to preventing skin cancer is protecting yourself from the sun, but too few people heed that advice: Skin cancer strikes more than a million Americans annually and is on the rise.

Now researchers have developed an experimental cream that may repair some sun damage and help ward off cancer. Consider it gene therapy in a bottle, a lotion containing an enzyme that repairs sun-damaged DNA.

Helps the most sensitive

It reduced the incidence of the most common form of skin cancer when tested on some of the world's most sun-sensitive people -- sufferers of a rare inherited disease called xeroderma pigmentosum, or XP, who can blister in minutes and suffer skin cancer at 1,000 times the rate of average people.

Might the cream, called Dimericine, also help the general population? Ultraviolet rays damage DNA the same way in XP patients as in anyone else. So this fall, researchers plan to take Dimericine to three sunny cities -- San Diego, Los Angeles and Jacksonville, Fla. -- to test it on 600 people who have had one skin cancer removed and thus are at a high risk for more.

Don't put away your sunscreen yet. Even if the cream ultimately works, it's not perfect and so wouldn't be a license to fry.

But "right now when someone forgets or misuses or washes off a sunscreen and has a sunburn, there's nothing that can be done for the long-term damage that's been done to the skin," says molecular biologist Daniel Yarosh, who created Dimericine.

Now that scientists have pinpointed UV-caused gene mutations, "sooner or later, there's going to be a morning-after cream" to help fix them, adds Yale University dermatologist Dr. David Leffell.

About 1.3 million Americans will be diagnosed with basal or squamous cell carcinoma this year, the most common skin cancers and the ones easily cut away if caught early, according to the American Cancer Society.

The deadliest skin cancer, melanoma, will strike an additional 51,000 Americans, a toll rising 3 percent a year. Skin cancer will kill almost 10,000 this year, the majority melanoma sufferers.

Start in childhood

The best protection is to limit sun exposure beginning in childhood, dermatologists say. Sunburns early in life are considered the most dangerous; doctors even have begun seeing melanoma in twentysomethings.

Slip on a shirt, slop on sunscreen and slap on a hat anytime you're in the sun, but especially between 10 a.m. and 4 p.m. when UV rays are strongest, says the cancer society's new "slip, slop, slap" sun-safety campaign.

And that's exactly what some parents and lifeguards do.

Ulrich, 20, says he is "almost religious" about applying the sunscreen each time he gets out of the water and several times throughout the day. He wears a cap and sunglasses to shield his face from the sun's rays.

"Sometimes we have to remind the parents to put sunscreen on their kids," he said.

But Jessica Grogg, a teacher at Christian School for the Young Years, said most parents provide a sunscreen with SPF of at least 15, and some as much as SPF 45 for the children who come swimming.

The day-care center applies sunscreen to the children each day after lunch, before the group leaves for the pool.

Skin does repair itself

But one burn doesn't mean cancer. Skin has complex repair mechanisms that remove about half of UV-damaged DNA in 24 hours, half the remaining damage in another day, and so on, Yarosh explains.

But over time, missed repairs build up. Enough built-up damage equals cancer.

Dimericine's developers are seeking Food and Drug Administration approval and will begin studies to see if it can prevent general skin cancer too.

Dimericine may be "a very important step forward," says Dr. Martin Weinstock, chairman of the cancer society's skin cancer advisory board. But for now, avoiding the sun is a proven, easy preventive, he stressed.

Hunter Lucas, 8, doesn't mind the smell or slimy feel sunscreen can give. His mother sends sunscreen for him to use while he's at the pool with Angels Aware day care.

"I don't care because I never get burned," said the brown-headed child, who already has a deep tan. "My mom always has to wear that."

Features editor Laura Johnston contributed to this report.