Skin surface electric potential as an indicator of skin condition: a new, non-invasive method to evaluate epidermal condition.

We previously demonstrated that the skin surface electric potential, which has been long recognized as a parameter of emotional or physiological state, is generated by epidermal keratinocytes and is strongly associated with the ion concentration gradient in the epidermis. Thus, at temperatures below the threshold of sweating, the potential provides a measure of the epidermal ion concentration gradient, which in turn is related to epidermal homeostasis and pathology. In the present study, we established a new, non-invasive method to measure skin surface electric potential. In healthy skin, calcium ion was localized in the uppermost epidermis and the gradation disappeared by tape stripping. Skin surface potential was also disappeared by tape stripping. Moreover, environmental humidity affected the potential, whereas temporary hydration of the stratum corneum did not affect it. These results suggest that the skin surface electric potential may be an indicator of the pathophysiology of the living layer of epidermis, and thus may be useful as a new parameter to evaluate skin condition.