Transepidermal water loss
Also called: TEWL
Transepidermal water loss, often shortened to TEWL, is the water that evaporates through the skin barrier. Higher TEWL usually means the barrier is losing water more easily.
At a glance
- TEWL is one way researchers measure how well the skin barrier holds water.
- A stressed barrier often has higher TEWL and feels tighter, rougher, or more reactive.
- Moisturisers can reduce water loss through humectants, emollients, and occlusives.
On this page
The short answer
Transepidermal water loss - TEWL if you enjoy skincare abbreviations - means water evaporating through the skin barrier.
Some water loss is normal. Skin is not cling film.
But when TEWL is higher than it should be, skin often feels tighter, rougher, drier, or more reactive.
Why TEWL matters
Researchers use TEWL as one way to understand barrier function. If the outer skin layer is disrupted, water escapes more easily.
A 2023 skin barrier review describes moisturisers as supporting barrier function through humectants, emollients, and occlusives, and notes improvements in transepidermal water loss in several moisturiser studies[1].
That is why TEWL shows up in barrier studies, dry-skin research, and rosacea-prone or sensitive-skin discussions.
It is not a trendy metric. It is a practical clue.
What can raise TEWL
Common reasons skin loses water more easily include:
- harsh cleansing
- over-exfoliation
- cold wind and indoor heating
- hot showers
- retinoids or acids introduced too fast
- active eczema, dermatitis, or other inflammatory skin disease
- skipping moisturiser when the skin is already tight
If your face stings from products that used to feel fine, the barrier may need a quieter routine.
How moisturisers help
A moisturiser review[2] explains the classic moisturiser categories: humectants attract and bind water, emollients smooth and soften, and occlusives reduce evaporation.
In normal routine language:
- humectants help water stay in the upper layer
- emollients make roughness feel smoother
- occlusives slow water from leaving
You do not need three separate products. A well-balanced moisturiser often does all three jobs.
The practical takeaway
If TEWL is the problem, the answer is usually less drama: gentler cleansing, moisturiser, sunscreen, and fewer irritating experiments.
Barrier care is not glamorous. It is the part of skincare that makes everything else more tolerable.
Keep reading
Dictionary
Skin barrier
Dictionary
Humectant
Dictionary
Emollient
Dictionary
Occlusive
Ingredient
Glycerin
Ingredient
Ceramides
Ingredient
Petrolatum
Ingredient
Dimethicone
Ingredient
Panthenol
Condition
Dry skin
Condition
Sensitive skin
Condition
Rosacea and redness
Guide
How to treat dry skin on your face without making it angrier
Guide
Best moisturizer for rosacea-prone skin: how to choose calmly
Guide
How to calm a rosacea flare without making it angrier
Common questions
What does TEWL mean in skincare?
TEWL means transepidermal water loss: water escaping through the skin barrier. Higher TEWL is often a clue that the barrier is stressed or dry.
How do moisturisers reduce TEWL?
Balanced moisturisers can bind water with humectants, soften the surface with emollients, and slow evaporation with occlusives.
Can I feel TEWL happening?
You do not feel TEWL directly, but high water loss often shows up as tightness, roughness, flaking, or stinging.