Celebrities, models and people who simply want to look fit spend days and often years baking, broiling and roasting in the sun to achieve a golden tan. But what kind of damage are those invisible UV rays doing to your skin?

"Your skin can appear up to 10 years older just by going in the sun without protection," says CAREN CONRAD, spokesperson for the Boscia skincare line.

To prove it, Caren invited several young women to sit under a Wood's Lamp skin scanner, which uses deep violet rays to expose hidden skin conditions, such as sun spots and permanent damage, that normally are not visible to the naked eye. The different skin lesions show up in varied shades of violet, with damage showing up as bright white.

One of the girls, VONNY FAUCHEUX, has been modeling for 14 years. She says she used to prepare for auditions by bronzing her skin while lying atop aluminum foil.

"I would sit on my rooftop in Louisiana and lay out aluminum foil and really attract the rays," she says.

But after seeing herself under the Wood's Lamp, Vonny is scared straight!

"It was shocking!" Vonny says. "It was kind of a wake-up call. I saw a lot of spots and things that were what's going to be visible in a few years."

Caren says the lamp acts like a "crystal ball to see what's coming in your future." "Sometimes you will see so much sun damage," she says, "that we do recommend that they go to the dermatologist and have it checked for skin cell cancer."

Caren recommends the Japanese Boscia line for skincare, and says that stars from GWYNETH PALTROW to ALICIA SILVERSTONE are fans of the cleansing and moisturing products.

"They're all using Boscia to condition their skin, keep it healthy."

For more star beauty tips, keep watching "The Insider."