Transepidermal Water Loss (TEWL) refers to the amount of water that passively evaporates from the skin’s surface into the external environment. It is a key indicator of skin barrier function.
TEWL stands for Transepidermal Water Loss, which is just a fancy way of saying how much moisture your skin naturally loses throughout the day. It’s one of the best indicators of how healthy and strong your skin barrier is.
Why it matters for your skin?
When TEWL is high, your skin is literally leaking moisture—leading to dryness, sensitivity, flaking, and irritation.
When TEWL is low, your skin barrier is doing its job: keeping hydration in and keeping irritants out.
Why skincare brands talk about TEWL?
Because reducing TEWL means:
- Softer, smoother skin
- Better long-term hydration
- Fewer flare-ups and irritation
- A stronger, healthier barrier
In simple terms
TEWL tells you how well your skin holds onto moisture—and improving it is the key to calm, glowing, resilient skin.