What is TEWL?
Trans-epidermal water loss (TEWL) is the passive evaporation of water through the skin. It is widely used as an indicator of skin barrier function: when barrier integrity is impaired, TEWL usually rises.
Think of skin like a watermelon rind.
When the surface is intact, the red core stays protected.
When the surface is damaged, water escapes more easily.
Protective skin barriers can help by adding a temporary outer layer, like replacing part of the rind to shield vulnerable skin and reduce excess water loss.
Illustrative TEWL Ranges (g/m²/h)
These values are approximate and vary with body site and measurement conditions.
Healthy intact skin
~5–10
Typical low TEWL, consistent with an intact barrier.
Dry / vulnerable skin
~7–15
May show mild increase, depending on severity and site.
Inflamed skin (for example, dermatitis / eczema)
~15–35+
Often shows clearly elevated TEWL, reflecting barrier disruption.
Recently closed or impaired wound/periwound skin
Often above intact-skin levels; may be ~20+
Higher TEWL can indicate incomplete barrier recovery.
Why this matters in wound care
When TEWL rises, the skin barrier is less efficient at retaining water and protecting tissue. In fragile or periwound skin, that can contribute to further breakdown if not addressed.
How to avoid becoming a “cut watermelon”
• use alcohol-free barrier film or advanced skin protectant when appropriate
• minimize unnecessary adhesive trauma
• manage exudate and maceration carefully
• support dry skin with suitable emollients
• reduce friction, heat, and prolonged moisture exposure
Protect the barrier. Protect the core. Support healing.
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