Author Affiliations: Washington University, St Louis, Missouri (Mr Brodell); and Dermatology Section, Departments of Internal Medicine and Dermatology, Northeastern Ohio Universities College of Medicine, Rootstown, and Department of Clinical Dermatology, Case Western Reserve University School of Medicine, Cleveland, Ohio (Dr Mostow).
Erythema ab igne (EAI), a netlike dermatosis, is caused by repeated exposure to moderate levels of heat (infrared radiation). Most seat heaters reach an upper limit of 43.0 °C (109.4 °F) with a deviation of about 1.8 °C (3.8 °F).1 Malfunctioning seat heaters have reached even higher temperatures, nearing 48.9 °C (120.0 °F), causing second-degree burns, especially in patients with mobility and sensory deficits.1,2 However, EAI can occur with chronic exposure to normally functioning heated car seats.
Brodell D, Mostow EN. Automobile Seat Heater –Induced Erythema Ab Igne. Arch Dermatol. 2012;148(2):264-265. doi:10.1001/archdermatol.2011.1158