It's short for trans epidermal water loss and is the natural process of water evaporating from your skin into the air. A healthy skin barrier keeps that water locked in — but when your barrier is compromised , TEWL skyrockets, leaving your skin dull, dehydrated, and more vulnerable to environmental damage. Think of your skin like a brick wall . Your skin cells are the bricks; your lipids are the mortar. If the mortar is weak, water escapes easily. That’s how TEWL quietly wea