This patient presented to me with a mottled, lacy red rash on her lower back. She had chronic lower back pain, and was using a heating pad every night to sleep. I diagnosed with her erythema ab igne (EAI). This is a skin reaction caused by chronic exposure to infrared radiation in the form of heat. It was once a common condition seen in the elderly who stood or sat closely to open fires, or electric space heaters. Although the introduction of central heating has reduced EAI of this type, it is still found in individuals exposed to heat from other sources. Other causes include application of hot water bottles or heat pads to treat chronic pain, repeated exposure to car heaters or furniture with built-in heaters, and occupational hazards for silversmiths and jewelers (face exposed to heat), bakers and chefs (arms).
Limited exposure to heat, insufficient to cause a direct burn, causes a mild and transient red rash resembling lacework, or a fishing net. Prolonged and repeated exposure causes a marked redness and discoloration of the skin. The skin and underlying tissue may start to thin (atrophy), and rarely sores may develop. Some patients may complain of mild itchiness, and a burning sensation.
For treatment, the source of chronic heat exposure must be avoided. If the area is only mildly affected with slight redness, the condition will resolve by itself over several months. If the condition is severe and the skin pigmented and atrophic, resolution is unlikely. In this case, there is a possibility that squamous cell carcinomas may form. If there is a persistent sore that doesn't heal or a growing lump within the rash, a skin biopsy should be performed to rule out the possibility of skin cancer.Treatment with topical tretinoin, or laser may improve the appearance.
Dr. Cindy N. Berthelot, M.D. is a board certified dermatologist treating patients in the greater Houston community, including Clear Lake, League City, Friendswood, Pasadena, Deer Park, Dickinson, Pearland, Alvin, Seabrook, Kemah, Webster, Galveston, Texas City, La Marque, and Santa Fe, Texas. To make an appointment with Dr. Berthelot, please contact us at 281.480.7272.