What Is TEWL? The Reason Skin Feels Tight by Evening
Transepidermal water loss: water leaving skin through its surface into the air. Higher in dry air, wind and heated rooms.
On the label
Never on a label. It is the idea behind every claim about locking in moisture.
What it does not mean
It does not mean skin is dehydrated in a medical sense. It is the everyday reason a face that felt fine at breakfast feels tight at dinner.