Erythema Ab Igne: A Clinical Review.

Erythema ab igne (EAI) is a skin condition caused by chronic heat-induced damage. The rash usually progresses over weeks to months of repeated or prolonged exposure to subthreshold-intensity infrared radiation that is not hot enough to cause a burn. The diagnosis is clinical based on patient history and physical examination, but a biopsy can reveal dilated vasculature, interface dermatitis, and pigment incontinence. Erythema ab igne initially was described in association with patients cooking over wood-fire stoves but has been shown over the decades to have a variety of causes. Herein, we describe various etiologies of EAI, including new heat-producing technologies, cultural practices, psychiatric illnesses, and even iatrogenic causes. However, the cause most commonly is application of heat for treatment of chronic pain, which may be a diagnostic clue for an underlying chronic illness. Although there are no current US Food and Drug Administration-approved therapies for treatment of EAI hyperpigmentation, the prognosis is excellent because removal of the heat source often will result in spontaneous resolution over time. Finally, chronic EAI rarely has been reported to evolve into squamous cell carcinoma, poorly differentiated carcinoma, cutaneous marginal zone lymphoma, and even Merkel cell carcinoma.