But some dermatologists say that slathering on shiny lip glosses can actually increase your risk of developing skin cancer. Of course, wearing any lip product without SPF doesn’t exactly shield the thin skin from sun damage. But the slick, shiny nature of the gloss could be making the sun’s UV rays hit harder, some experts say.

“These lip glosses can make more of the light rays penetrate directly through the skin instead of getting reflected off of the skin’s surface,” says Dr. Christine Brown, a dermatologist at Baylor University Medical Center in Dallas. (You're covered, however, if you wear lip gloss with SPF.)

At worst, say some dermatologists, the resulting sun damage can lead to potentially fatal forms of skin cancer. An estimated 3,500 new cases of skin cancer of the lips are diagnosed each year, and 90 percent of those cancers are squamous cell carcinoma. While that form of cancer isn't usually particularly serious, it can be more aggressive on the lips than on other parts of the skin. If left untreated, it can cause disfigurement, and in very few cases, it can spread to other organs and become deadly.