Laptop users should not, apparently, rest their computers atop their laps. That's the upshot of a new Swiss study which has concluded that repeated exposure to the heat of a laptop can give your thighs a permanent rash known as "toasted skin syndrome." (Watch a local report about the condition.) An instant guide:

What is "toasted skin syndrome"?
An "unusual-looking mottled skin condition" caused by long-term heat exposure, and more commonly cited in reference to industrial bakers and glass blowers. In a study newly published in the journal Pediatrics, researchers from Basel's University Hospital outline the case of a 12-year-old boy who regularly played video games for hours a day while resting a laptop on his thighs. As in 10 similar cases documented in medical journals over the past six years, the boy developed the telling "sponge-patterned" skin discolorations. 

Is the syndrome dangerous?
It's mostly harmless, say the researchers, although it can cause "permanent skin darkening" and, in rare cases, increase the risk of skin cancers.

Is it ever safe to use a laptop this way?
Most major manufacturers discourage users from positioning laptops on their legs or knees for more than a few minutes at a time. Or as The Awl put it: "Don't keep [the computer] on your lap past the point where you feel like your thighs are on fire."

What other injuries can a laptop cause, if used this way?
This ill-advised laptop habit can raise the temperature of a man's scrotum by almost 3 degrees according to a 2004 study by the State University of New York, lowering his sperm count. More recent warnings from doctors at the University of North Carolina list other potential consequences, including headaches, back, and spinal injuries, and carpal tunnel syndrome. "When you use a laptop, you have to make some sort of sacrifice," said Dr. Kevin Carneiro, one of the study's authors. 

Sources: MSNBC, CNET, Yahoo News, MSN