What is transepidermal water loss (TEWL)?

Transepidermal water loss (TEWL) refers to the process through which water evaporates from the skin's surface into the atmosphere. This phenomenon primarily occurs through the stratum corneum, the outermost layer of the skin, which acts as a barrier to water loss but is also permeable to some degree. When TEWL is elevated, it can lead to dryness and compromise the skin barrier function, resulting in various skin issues such as irritation, inflammation, and increased sensitivity.

Understanding TEWL is essential for skin care professionals, as it emphasizes the importance of maintaining skin hydration and barrier integrity. By assessing the factors that contribute to TEWL—such as environmental humidity, skin condition, and the use of various topical products—practitioners can better tailor their skincare regimens to help minimize water loss and maintain optimal skin health.

The other options do not accurately define TEWL. The increase of water within the deeper skin layers indicates hydration rather than loss, retention of moisture due to humidity refers to external environmental factors that may aid in retaining moisture rather than losing it, and absorption of oil by the skin describes a different process entirely not related to water loss.