Which radiation produces an erythema ab igne?

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

Answer: (B)

Erythema ab igne comes from chronic exposure to heat, specifically infrared radiation. When skin is repeatedly heated over a period of time, the heat damages superficial blood vessels and the skin, producing a persistent reddish, netlike (reticular) pattern with later hyperpigmentation. Infrared radiation is the form of energy responsible for this heat exposure, which is why prolonged contact with heat sources like heaters or heated objects can lead to this condition.

Ultraviolet radiation, by contrast, causes sunburn and photochemical skin reactions, not the chronic heat-induced pattern of erythema ab igne. Minimal erythema refers to the mildest UV-induced redness, while second-degree erythema denotes a more severe burn. The distinctive feature of erythema ab igne is its origin in chronic heat exposure rather than UV-induced phot damage.