A study was made on 15 healthy subjects to evaluate the efficacy of water immersion with commonly used raw materials on skin elasticity, viscoelasticity and hydration of stratum corneum.
Samples used in this study included 30, 60, 90g of sodium hydrogen carbonate and 60g of bath preparation containing 90% in weight of sodium hydrogen carbonate (Cool Bathcrin^®). These samples were dissolved into 200l of plain water kept at a temperature of 41°C. The duration of each bathing was 5min.
Skin elasticity (skin distensibility), skin viscoelasticity and hydration of stratum corneum improved in all types of water immersion including plain water immersion. The skin distensibility, viscoelasticity and hydration state showed a statistically significant increase after water immersion with sodium hydrogen carbonate as compared with those before water immersion. In the plain water immersion group, no significant differences were observed between the values before and after water immersion with the exception of skin hydration. However, a significantly higher rate of increase in skin hydration was observed in the groups of water immersion with sodium hydrogen carbonate as compared with the plain water immersion.
The above results show that alkaline salt, especially sodium hydrogen carbonate, improves skin distensibility, viscoelasticity, and hydration state. Furthermore, we recommend sodium hydrogen carbonate as one of the most useful components of bath preparation because it provides the suppleness, freshness, and smoothness of stratum corneum.