Erythema ab igne is a skin condition that can be caused by resting a laptop computer on the thigh or belly and using it for a while.

As CPU and GPU can heat at 40 or 50º Celsius, it will produce a burn in the skin that is painless and not always cause a color change, so it may go unnoticed. If the situation continues it can produce a permanent scar, and eventually evolve to skin cancer.