The main function of the dermal barrier is to protect us against the penetration of contaminants and micro-organisms. It also prevents our body from drying out. Analysis of the properties of this skin barrier is important in various fields of medical treatment and cosmetology. The development and improvement of topically applied substances require an objective analysis of its characteristics.
The amount of water evaporated through the skin can be measured and used for characterizing the epidermal barrier function. If the dermal barrier is damaged, more water can evaporate on the skin than in the case of an intact barrier. Transepidermal water loss (TEWL) measurement is the standard method to characterize epidermal barrier function. However, these measurements have the disadvantage that they are influenced by topically applied substances containing water as a component of the mixture. Additionally, TEWL measurements must always be performed under standardized climatic conditions and they can be affected by anxiety or instability of the patient or proband during the measurements.
In vivo laser scanning microscopic measurements (LSM) represent a reasonable alternative method. A team led by Jürgen Lademann at the Charité University Hospital Berlin (Germany) carried out a study comparing TEWL and LSM measurements. Additionally, the skin elasticity and the stratum corneum hydration were analyzed. The investigations were performed prior and subsequent to a 4 week treatment of dry skin with a gel mixture, developed for skin treatment after radiotherapy for cancer.
The results indicate that in vivo laser scanning microscopy is an appropriate method for the characterization of the skin barrier structure without interference by external factors. It gives a more detailed and in this setting a more accurate evaluation of the state of the skin barrier than TEWL measurements. Furthermore, LSM measurements are suited to analyze the efficacy of topically applied medical drugs and cosmetic products on the cellular level.