LONDON, England (Reuters) -- Laptops have always been a hot item but a 50-year-old scientist did not realise to what extent until he burned his penis.

The previously healthy father of two remembered feeling a burning sensation after he had been writing a report at home for about an hour with the computer on his lap.

He noticed a redness and irritation the following day but it was not until he was examined by a doctor that he realised how much damage had been done.

"The ventral part of his scrotal skin had turned red, and there was a blister with a diameter of about two centimetres (0.8 inches)," Claes-Gorn Ostenson, of the Karolinska Institute in Sweden, wrote in a letter published in The Lancet medical journal on Friday.

Two days later, the blisters broke and the wounds became infected and then crusted but after about a week the unidentified scientist was "healing quite rapidly."

Ostenson noted that the computer manual did warn against operating it directly on exposed skin but said the patient had lap burns even though he had been wearing trousers and underpants.

"This...story should be taken as a serious warning against use of a laptop in a literal sense," he added.