The relation between constitutional skin color and photosensitivity estimated from UV-induced erythema and...

In 54 healthy volunteers we assessed predictors of sensitivity to ultraviolet (UV) light, including Fitzpatrick's sun reactive skin types and constitutional skin color, and compared these with one another and with responses of the skin to UV irradiation, as determined experimentally by a minimal erythema dose (MED), a minimal melanogenic dose (MMD), and dose-response curves for UV-induced erythema and pigmentation. For these studies, a xenon arc solar simulator was used as the source of UV irradiation, and a chromameter interfaced with a computer for objective measurement of UV-induced erythema and pigmentation was employed. The skin type did not correspond well to the constitutional skin color, as measured by a chromameter prior to UV irradiation. Within each skin type, there were large ranges of MED and MMD values and great variability in the shapes of the dose-response curves. Constitutional skin color was also not a good predictor of the measured MED and MMD values but did appear to correlate with the steepness of the dose-response curves for erythema and for pigmentation. From these studies, we propose that objectively measured constitutional skin color is a better predictor of UV responses of the skin than skin type and that steepness of dose-response curves for erythema is a better measure of the response of the skin to UV irradiation than is a MED measurement.