• skin physiological properties;
  • non-invasive measurement;
  • stratum corneum hydration;
  • skin surface pH;
  • melanin;
  • elasticity;
  • sebum


The invasive measuring techniques are of great help in the evaluation of skin physiological functions and topical formulation. The reproducibility and accuracy of the instrument are crucial.


The aim of this study is to reveal the differences and correlations in measuring skin hydration, pH, sebum, elasticity and melanin on the forearm or faces between two commercially available series of instruments.

Materials & Methods

20 subjects were enrolled to be measured by the two series of instruments. The measurements by each series were performed on the left/right side of the body randomly. The pH, sebum, elasticity and melanin measurements were performed on the faces in different areas, while the hydration measurements were operated on the forearms before and after wet dressing, respectively.


Positive correlations were found in the values of skin SC hydration, pH, sebum and melanin detected by the two series. The values related to skin elasticity measured by the two instruments were statistically negative correlated. The Soft Plus series has higher variation in detecting skin hydration, pH, and melanin than the instruments from Courage & Khazaka.


The differences of the two series must be instrument related. The difference in level of measurement can be due either to differences in the design of the probe, to differences in time for measurement, to differences in left/right part of the body or a combination of these three.


The two series have significant correlations. The instruments from CK are more reproducible.