5 October 2010 Last updated at 06:33 ET

'Laptop thigh' skin rash warning

The toasted skin rash was caused by prolonged use of a laptop

It may be called a laptop, but there could be a price to pay for using it on your lap regularly, say doctors.

The heat generated by the underside of the machine is enough to cause a nasty rash, especially if used against bare skin for hours at a time.

The journal Pediatrics reported the case of a 12-year-old who developed discoloured skin after playing games for hours.

The rash should cause no lasting ill-effects, said a UK dermatologist.

Toasted skin

The full name for the condition is erythema ab igne, and used to be common in people exposed to heat as part of their work, such as bakers and silversmiths.

It is sometimes seen in elderly patients who use hot water bottles to keep warm.

But now the condition, also called "toasted skin syndrome", is being seen in some laptop users.

Laptops can raise the temperature of parts of their case to above 50 degrees Celsius.

If left in contact with skin, this can result in a mottled appearance which does not immediately disappear, even after the machine has been removed.

In more serious cases of erythema, the skin can be left darkened, although not usually permanently.

The study by researchers at University Hospital Basel is not the first to note this problem. Other reported cases in medical journals included an American law student who spent six hours a day with her computer resting on her lap.

Dr Bav Shergill, a consultant dermatologist at Brighton University Hospitals NHS Trust, said that people who developed the rash should not be overly concerned.

"I would expect it to resolve fairly quickly, with no long term consequences.

"It's the same condition I used to see as a junior doctor in elderly ladies who spent all day sitting too close to electric bar fires.

"If you use a laptop like this every day, there could be discolouration, but even this should clear up."