Bioengineering Analysis of Water Hydration: An Overview

Skin hydration depends on the water-holding capacities of the stratum corneum. One of the techniques used to evaluate skin water content is the water sorption-desorption test. This method involves hydrating the skin with water and then observing the subsequent dehydration activity by means of serial recording with electrical instruments. Currently, three instruments are available to perform such a test: the Skicon® 200, the Corneometer® CM820 and the Nova DPM® 9003. However, each device measures the skin hydration in its own unique parameter, making interexperimental comparisons difficult. Despite this shortcoming, the water sorption-desorption test is a useful tool to measure the dynamic hydration of the skin and the stratum corneum water-holding properties. Pathological skin conditions like atopic dermatitis affect corneum integrity and reduce its ability to hold water. Irritants can also damage the cutaneous barrier and result in decreased hydration. On the contrary, delipidization of the newborn skin with organic solvents increases the water-holding capacity of the stratum corneum. Since the superficial lipid layer covering the skin surface of the newborn limits the sorption of water, its removal allows more water to be absorbed, resulting in a higher water-holding capacity than before. These results have all been determined using the water sorption-desorption test. While the studies produce significant information on skin hydration kinetics, the data are reported in different units. As such, it is difficult to make comparisons between sets of experiments where different electrical instruments are used. Finding a standard parameter unit for measuring skin hydration will benefit dermatological research greatly and allow the results obtained from one instrument to aid in the interpretation of those from another instrument. The high degrees of correlation that exist among the Skicon 200, Corneometer CM820 and Nova DPM 9003 may be the key to future developments of a standardized parameter unit.