Erythema ab igne (EAI), also known as hot water bottle rash,[2] is a skin condition caused by long-term exposure to heat (infrared radiation).[3] Prolonged thermal radiation exposure to the skin can lead to the development of reticulated erythema, hyperpigmentation, scaling and telangiectasias in the affected area. Some people may complain of mild itchiness and a burning sensation, but often, unless a change in pigmentation is seen, it can go unnoticed.