These folks are having fun in the sun — but they could be risking their health in the process.

“Sunburn tattoos,” a body-modification trend that first tried to happen in 2015, is heating up for the summer 2019 season, according to a new Inked Mag report.

It works like this: People place stencils on exposed skin and head outside to soak up some rays. When that mission is complete, they remove the stencils to reveal “semi-permanent” designs in paler skin tones.

The practice originated with a French artist named Thomas Mailaender, Inked Mag reports. His “Illustrated People” series involved placing photo negatives onto models’ skin, then shining an ultraviolet light onto them. The process created contrast on the skin. A portrait of a man on a horse was burned onto a woman’s back; an image of a child was singed into a man’s right arm.

It wasn’t long before #sunburntattoo posts were bubbling up on Twitter and Instagram — and we are not just talking tan lines here, people.

Social-media users are feeling the burn via designs of spiders, the Batman logo and the Playboy bunny. In an image and caption uploaded last year, one Instagram user named Paloma Ponce wrote that she got a dreamcatcher-shaped sunburn tattoo by applying a stencil on her skin, then going out into the sun and later removing the stencil.

Another Insta user, @sch_nien, in an image also shared last summer, shows a man’s burned leg with pale patches that say “sun” and “shine” separated by the shape of a sun.

Experts often stress the importance of protecting skin from the sun’s powerful rays.

“Both UVA and UVB [rays] can cause harmful effects on the skin,” says Dr. Mary Stevenson, a dermatologic surgeon and assistant professor at NYU Langone.

“Ultraviolet causes damages to cellular DNA, with UVB damaging the basal layer of your skin predominantly and UVA penetrating deeper and also causing damage which can ultimately result in skin cancer,” Stevenson adds. “Blistering sunburns in particular, which result from intense ultraviolet exposure, are known risk factors for causing cancer. As a dermatologic surgeon, I treat skin cancers daily and advise my patients to avoid burning and to wear a physical blocker with titanium or zinc oxide.”

So play it safe this summer: As the Fun Tan Tattoo stencil brand suggests, opt for a layer of sunscreen or self-tanning cream instead of temporary embellishments with consequences you may regret down the line.