The Effects of Subacute Sunlight Exposure on Skin Thickness: A Pilot Sonographic Study

We investigated the effects of sunlight exposure on dermis and skin thickness. High-frequency ultrasound (US) was used to assess changes over 3 weeks of natural sunlight exposure. For intra- and inter-rater reliabilities, repeated dermis/skin thickness measurements on two consecutive days in 11 healthy adult subjects were assessed independently by two physiatrists. In the second part, seven adult volunteers were examined before and after a 3-week seaside vacation to evaluate the effects of subacute sunlight exposure on dermis/skin thickness. Measurements were taken over the forehead, forearm, and umbilicus. Intra-rater intraclass correlation coefficients (ICCs) were good to excellent (0.871-0.998) for nearly all measurements, except forehead total dermis/skin thicknesses for both raters. Inter-rater ICCs were also good to excellent (0.796-0.995), except for forehead dermis/skin and forearm dermis/skin thicknesses on the 1^st and 2^nd days. Following sunlight exposure, significant decreases were observed in forehead upper dermis/skin and soft tissue, forearm skin, and umbilicus dermis/skin thicknesses (all P < 0.05). Our preliminary results suggest that subacute sunlight exposure appears to decrease skin thickness. High-frequency US proved to be a reliable noninvasive tool for skin assessment.