Transepidermal Water loss (TEWL) is a something you need to know about especially if you wanna get more into taking care if your skin and purchasing skincare. Transepidermal water loss refers to the loss of water that passes through the epidermis and evaporates into the air. Our skin is composed of multiple layers: the epidermis (top), dermis (middle), and hypodermis (bottom). The epidermis is the outermost layer of skin (the one you see when you look in the mirror). TEWL is a natural process that happens to everyone. It’s your skin’s way of regulating its water content(your skin is a organ). However, TEWL can be made worse by things like trauma to the skin, such as a sunburn or a case of eczema, weather, and skincare or makeup products that are to drying can negatively affect TEWL levels.