Variation of skin properties within human forearms demonstrated by non-invasive detection and multi-way analysis

Background: It is known that the properties of human skin vary locally. The purpose of this study was to investigate the properties of human volar forearms even further using advanced non-invasive techniques and numerical methods. Methods: The skin properties of human volar forearms were investigated using measurements of trans epidermal water loss and multifrequency electrical impedance. Eight sites on the forearms of 27 healthy volunteers were measured. The sites were oriented as squares, four sites on both left and right forearm, approximately 40-50 mm apart. Results: Analysis of variance showed significant differences for epidermal water loss (P < 0.01) and the skin impedance (P < 0.001) between the inner and outer sides of the arms. Additionally, parallel factor analysis of the full skin impedance spectra also showed that there are systematic differences between right and left arm (P < 0.01). Conclusions: It is crucial to design skin studies carefully in order to minimise the effects of the local skin properties of human skin.