Analysis of the microtopography of the skin by silicone replicas after repeated exposure to actinic radiation at high altitudes

We investigated the superficial microtopography of the normal skin of 11 volunteers (not exposed to sunlight during the last 4 months), before and after sun exposure for 5 days at high altitudes of 2900-4559 m. The experiments were carried out on Mount Rosa in Italy, and cutaneous replicas using silicone resin were taken every day after 7 h of sun exposure. Casts were taken from the forehead, glabella, dorsum nasi, radial side (protected with a cream SPF 9.72) and ulnar side of the back of the hands, the only areas not protected. A total of 422 replicas were metallized with gold-palladium and observed under Zeiss 940A scanning electron microscope. The images were elaborated and analysed on computer with appropriate software supplying geometrical features of cutaneous surface using parameters proposed by Takahashi (1994). A Student's test for paired series was used to analyse the differences before and after 1-5 days of exposure giving uniform and significant data compared with controls. Using cutaneous replicas we demonstrated that repeated exposure of skin to sunlight in a short time elicits temporary defence mechanisms with increased obstruction of cutaneous pores, deepening of primary cutaneous furrows and shallowing of part of the secondary furrows; the two latter alterations are the consequence of reactive oedema.