Consistently warm areas included the nasolabial fold, external ear canal, hair-bearing areas of the scalp, and the beard and mustache in subjects who had facial hair. By contrast, the cheek, nose, earlobes, and chin were consistently cooler. This occurred in all subjects, regardless of age and sex. There was a striking correlation between the warmer areas of the face and the distribution of lesions in SD, as described in standard texts. Using an ultrasensitive thermal imaging device originally developed for military use, we found that there is a striking heterogeneity in the temperature pattern of facial skin.
Some areas are substantially and consistently warmer than others.
Areas of relative warmth include the nasolabial folds, external ear canal, hair-bearing areas of the scalp, and the beard and mustache in subjects with facial hair, while cool areas include the cheeks, nose, earlobe, and chin. The areas of relative warmth were unrelated to pathological skin conditions, since none of these subjects had any evidence of facial or scalp dermatitis. This extended to hair-bearing scalp, which becomes cool when hair is lost. Of interest is that SD clears in hair-bearing areas that become bald. The reason that high skin temperature seems to favor the appearance of SD lesions is unknown.