Which radiation yields an erythema ab igne?

• A. Ultraviolet radiation
• B. Minimal erythema
• C. Second-degree erythema
• D. Infrared radiation

Answer: (D)

Erythema ab igne arises from chronic exposure to heat in the infrared range. Repeated infrared heating damages superficial skin vessels and pigment-producing cells, producing a characteristic reticular, pigmented eruption often described as toasted skin syndrome. This is a heat-related pattern, not an acute sunburn, and it can develop from prolonged contact with heat sources like heating pads, hot-water bottles, or laptops. Ultraviolet radiation causes sunburn and a different pattern of skin change, not the reticular hyperpigmentation seen with erythema ab igne. Terms like minimal erythema relate to UV-induced skin reddening rather than a type of radiation or a heat-induced condition, and second-degree erythema isn’t a standard description for this pattern. The key idea is that this condition is linked to chronic infrared (heat) exposure.