Hot pop brown spot: erythema Ab igne induced by heated popcorn.

Erythema ab igne is caused by chronic heat exposure and presents with reticulated pigmentation. Although various causes of erythema ab igne have been reported, in the United States, its incidence has been declining due to the advent of central heating. When seen, it is usually in the setting of local applications of a heated source, such as a hot water bottle, to treat muscular or arthritic pains. We report a novel cause of erythema ab igne occurring in a patient with chronic arthritic pains. This patient applied popcorn kernels, heated in a microwave, to his right wrist and knee for 30 minutes at a time for over four months.