Full-body skin mapping for six biophysical parameters: baseline values at 16 anatomical sites in 125 human subjects

The skin, as the outermost organ, protects against exogenous hazards (outside-in barrier) and prevents the loss of essential parts of the body (inside-out barrier). The epidermal barrier exerts several functions with specific morphological elements. Regional differences in skin functions are well known. The aim of the present study was to assess and compare skin physiological parameters in vivo at 16 anatomical sites: Barrier function in terms of transepidermal water loss (TEWL), stratum corneum (SC) hydration (assessed by capacitance), skin surface pH, skin surface temperature, erythema index and skin pigmentation were quantified at 16 anatomical sites under basal conditions. In addition, casual skin lipid level as a function of sebaceous lipids was measured on the forehead.

The 6 functions at the 16 anatomical sites were assessed in a cohort of 125 volunteers working in the food processing industry. These functions were quantified with noninvasive instruments, namely a Tewameter (barrier function), a Corneometer (SC hydration), a pH-meter, a Mexameter (erythema index and pigmentation), a skin surface thermometer and a Sebumeter (casual sebum level).

We identified ranges for the 16 anatomical locations for each instrument and some parameters could be classified into distinctive groups. Furthermore, a left-right comparison was performed at 3 sites (dorsal hand, ventral hand and ventral forearm). Certain side differences could be shown for SC hydration, surface pH, erythema index, melanin index and skin surface temperature in the 3 assessed areas. A left-to-right, statistically nonsignificant difference was also established for TEWL.

The detected site-specific characteristics could be attributed to factors such as occlusion, different degrees of UV exposure, microcirculation and distribution of afferent and efferent nerve endings as well as fat distribution. External factors, such as life style, UV exposure and working conditions need to be taken into account. The present data are intended for an adequate selection of parameters and anatomical locations when assessing working conditions and designing clinical dermatological and pharmaceutical studies.