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Erythema ab igne represents a skin condition caused by exposure to open fire. It is sometimes called toasted skin syndrome, with the rash called fire stains. Exposure to infrared radiation creates a mottled appearance on the skin, usually appearing as blotchy, red, lacy patterns. After long-term and repeated exposure to heat, erythema ab igne might produce permanent discoloration of the skin and lead to skin cancer.
The condition commonly appears in people who use hot water bottles or electric heating pads to treat pain. Frequent use of these items might damage upper layers of skin similar to the harm seen by repeated exposure to the sun. It might take decades before the damage shows up as skin cancer. Doctors who treat patients with erythema ab igne typically look for underlying causes of pain in patients who rely on external heat to relieve discomfort.
This condition commonly appears more often in people working in certain occupations. Chefs who cook for hours over hot stoves might develop the rash on their arms. Bakers exposed to hot ovens in their work typically see the rash appear on the face. It also occurs in people who work as glass blowers and silversmiths.
Before central heating became common, toasted skin syndrome typically appeared on the legs after people sat in front of open fires to stay warm. The rash often showed up on the inner thighs after exposure to infrared radiation. In modern times, erythema ab igne might develop on the upper thighs of people who use laptop computers for prolonged periods of time. Sufficient heat is generated by some laptops to produce symptoms of this condition.
The disorder sometimes appears in patients who undergo ultrasound treatments as part of their physical therapy. Devices that emit high-frequency waves along with rapid vibrations produce heat that could lead to erythema ab igne in some patients. Infrared lamps used to treat pain might produce similar reactions.
Skin might first appear reddened, with a mottled pattern that blanches when pressed. After long-term exposure to open fire or heat, the exposed skin might turn brown, blue, or purple and no longer blanches. Skin tissue might get thin, and sores can appear in rare cases. Some patients complain of itching or burning in areas affected by the rash.
Treatment of erythema ab igne usually involves ceasing exposure to the heat source. In mild cases, the rash typically goes away within a few months. If prolonged exposure results in hyper-pigmented skin, ointments of retinoic acid with hydroquinone or laser treatment might fade the discoloration. When damage is severe, the skin may never return to its normal shade.