Laptop induced dermatitis also  known as toasted skin syndrome  is a reticulated darkening of the skin. In medical terms it is called erythema ab Igne.

Erythema ab igne (from Latin language meaning “redness from fire”) is a localized, reticular, pigmented, asymptomatic dermatosis due to prolonged, repeated, long-term exposure to submaximal head with infrared radiation (in the range of 43°C-47°C, insufficient to produce a direct burn).

Different are sources of heat that people may be exposed to, but the use of laptop computers, increased manifold in last years, has added a new cause, in consequence of the fact that often they are placed in contact with the skin of the thighs during use.

Because the heat produced by a computer may reach 44°C, the frequent use of a laptop is enough to cause erythema ab igne.

Computer-induced heat lesions are typically found on only 1 leg, normally on the left leg because the optical drives of laptops are located on the left side. Other possible heat sources are the battery and the ventilation-fan exhaust.

The computer placed on a lap may completely or partially occlude the ventilation-fan exhaust, which then may even increase the computer's temperature.

Patient should be advised to cease  placing the laptop directly in contact with the skin.