Skin Colour Changes in Psoriasis. Effect of UV Light Irradiation

Abstract

The change in colour of clinically unaffected psoriatic skin resolving concomitantly with distant sites of UV-irradiated psoriatic lesions was measured by a spectrophotometer. Skin colour was compared between psoriasis and an area of unaffected skin on a limb protected from UV light while the rest of the body received conventional treatment with UV light. Initially, there was a rapid loss of hue (represented by a flattening of the spectrophotometric curve) while unaffected skin showed elevated measurements which persisted during the course of treatment and subsided slowly for up to 2 weeks after cessation of UV light treatment. Clinically undetectable psoriatic lesions showed persistently raised spectrophotometric measurements for up to 10 weeks after cessation of treatment. This report suggests that a systemic factor stimulated or released by whole body UV light irradiation concomitantly influences the resolution of psoriatic lesions protected from the local effects of UV light.

The objective evaluation of the severity of psoriatic scales with desquamation collecting tapes and image analysis

“…The Mexameter ® evaluates skin color as the erythema index (EI) and the melanin index (MI). These skin color parameters have been used to assess the severity of psoriasis (7–10) and other inflammatory dermatoses (11, 12). The Cutometer ® has been used widely for non‐invasive measurements of skin elasticity (6).…”