Danielle Macaluso was a 30-year-old communications executive for L'Oreal Paris working on the launch of a sun-care product line three years ago when she made a discovery close to home professionally and personally – a mole that turned out to be melanoma.

Fortunately, treatment worked for the VP-communications of L'Oreal Paris, who is in remission. But her experience led her to realize how big an issue melanoma is as the third most common and one of the fastest-growing cancers in the U.S., with incidence having tripled in 30 years.

Her story became the impetus for L'Oreal Paris to lend its decades-old tagline to the It's THAT Worth It public-service announcement campaign, in partnership with the Melanoma Research Alliance, with work from L'Oreal's ad agency McCann and PR shop TogoRun. Ms. Macaluso appears in the campaign alongside some big-name talent, including Eva Longoria, Lea Michele and Diane Keaton.

The goal: Get people to wear sunscreen every day. That obviously helps L'Oreal, though it's a relatively a relatively small player with less than 4% of the $1.1 billion U.S. mass market for suntan lotion and oil, according to IRI.

It would be a much bigger business if people followed advice from the MRA and other skin-cancer groups. The Skin Cancer Foundation recommends people 6 months or older use an ounce of sunscreen daily, which would amount to more than 100 billion ounces annually in the U.S. But based on data from IRI, stores sold less than 1% that amount in the 52 weeks ended March 23. Even given that the IRI doesn't cover some club, department and other stores that sell sunscreen, the U.S. is still well behind recommended usage and falling further: Unit sales dropped 3.5% the past year.

Ms. Macaluso got melanoma despite always using sunscreen at the beach, she says in her ad. And despite millions of dollars of skincare advertising from L'Oreal and others, she said not enough focuses on the industry's most important benefit -- preventing skin cancer.

"We really as an organization felt we needed to work to educate young women about the importance of wearing sunscreen every day," she said.

"We know not to smoke," said TogoRun CEO Gloria Janata. "We know not to text while we drive. We really need to know to use sunscreen."

It's unusual, maybe unprecedented, for a marketer to include its tagline in a PSA effort. But while the tagline adds an element of L'Oreal branding, Ms. Macaluso said, "Our campaign is not overly branded." The company wanted the focus to be on the importance of daily sunscreen use and get people to share the message, she said. Realistically, competitors other than L'Oreal – such as Energizer Holdings' Banana Boat, Merck & Co.'s Coppertone and Johnson & Johnson's Neutrogena, stand to gain more from increased product use.

L'Oreal is turning to the Thunderclap crowdsourcing tool to sign up people to send a synchronized message about Its THAT Worth It and wearing sunscreen on May 20 at 5 p.m. The company, which is already donating $750,000 to the MRA for research, will make an additional donation of $1 for each Thunderclap signup or L'Oreal Paris Advanced Suncare product purchase in the U.S. up to $250,000 in 2014.