Transepidermal Water Loss (TEWL)

Abstract

The epidermal barrier is the outermost part of our body, or more precisely, of our skin. Approximately 90 % of the barrier function can be attributed to the stratum corneum. The importance of the epidermal barrier and more specifically the stratum corneum with its major components the corneocytes, the intercorneal bilamellar lipids, and the cornified envelope has become increasingly evident over the last years.

Skin as a barrier prevents the organism from loss of essential components such as ions, water, and serum proteins. The skin barrier also reflects internal processes, diseases, disease activity, and some of the lifestyle, manifested in intrinsic and extrinsic aging. It also has sociocultural functions and plays an important role in communication and self-expression. Transepidermal water loss (TEWL) is one of the most important parameters to evaluate the epidermal permeability barrier function of the skin. A low TEWL is generally a characteristic feature of an intact skin protective function. There are different methods for TEWL measurement, the unventilated (closed) chamber method, the ventilated chamber method, and the method using an open chamber. This chapter is mainly focused on the latter. To perform accurate and reliable measurements, variable factors related to the panelists, environment, and the instrument should be taken into account and will be addressed in this chapter.