The changes of skin surface hydration state were measured in vivo to evaluate the efficacy of bath preparations and their common use raw materials, following five samples, from a view point of moisturizing effect using High Frequency Impedance Measurment (3.5MHz.) as an empirical approach previously adopted by Tagami et al.
The temparature of water immersion was 41°C and the duration was 5min. Five kinds of samples used in this survey, 15 and 30g of sodium hydrogencarbonate, bath preparations containing 85% of sodiumu hydrogen carbonate, 2% of JOJOBA OIL, and 5% of dextrin were dissolved into plain water equipped with the maintenance of water temparature at 41°C, respectively.
As the result of this examination, these five samples enhanced the hydration state of stratum corneum after immersion and the value of skin surface hydration state showed high significant difference comparing to plain water. Especially, sample A immersion (containing 2% of JOJOBA OIL; Fig. 1) showed clear cut difference to compare to plain water immersion. (P<0.01 at 30, 60, 90, and 120min, after immersion)
These data suggested that JOJOBA OIL, dextrin and sodium hydrogen carbonate can be utilized effectively as a moisturizing factor for various types of bath preparations. It was proved that JOJOBA OIL, dextrin, and sodium hydrogen carbonate as raw materials of bath preparations possess the moisturizing effect after immersion through this survey.
We suppose that these raw materials might be concerned in the quantity of secondary bound water which is necessary to retain the suppleness and smoothness of stratum corneum, and propose that High Frequency Impedance Measurement (3.5MHz) is a suitable method to evaluate the hydration state of stratum corneum after water immersion.