Insensible Water Loss (TEWL): What Is It?

Definition of TEWL

Insensible water loss corresponds to the passive evaporation of water contained in the deeper layers of the skin to the outside, without being noticeable. Unlike sweating, it does not depend on the activity of sweat glands and occurs continuously, even at rest.

 

This phenomenon mainly occurs at the level of the epidermis, and more precisely the stratum corneum, which acts as a protective barrier. When this barrier is intact, water loss remains moderate and physiological. However, when it is damaged, TEWL increases, leading to drier skin, increased sensitivity, and sometimes irritation.

The role of the skin barrier

To understand TEWL, it is important to look at the structure of the skin. The stratum corneum is often compared to a “brick wall,” where the cells (corneocytes) are the bricks, and the lipids (ceramides, cholesterol, fatty acids) act as the mortar.

 

This system limits water evaporation while preventing the entry of external agents (pollutants, allergens, microorganisms). When this skin barrier is weakened, for example due to environmental factors, inappropriate care, or skin conditions, water escapes more easily.

 

Therefore, TEWL becomes a key indicator of skin integrity: the higher it is, the more the skin barrier is damaged.

 

Why does insensible water loss increase?

Several factors can influence insensible water loss.

Cause #1: Environmental conditions

Cold, wind, heat, or even overly dry air (heating, air conditioning) promote water evaporation. In winter, for example, TEWL often increases, which explains the feeling of tightness.

Cause #2: External aggressions

Harsh cleansers, excessive exfoliations, or certain irritating active ingredients can damage the skin barrier. This leads to an increase in TEWL and progressive dehydration.

Cause #3: Age

With aging, lipid production decreases. Your skin becomes thinner, more fragile, and less effective at retaining water, naturally increasing TEWL.

Cause #4: skin conditions

Certain conditions like eczema, psoriasis, or atopic dermatitis are associated with a damaged skin barrier. TEWL is often significantly higher in these cases.

Cause #5: lifestyle habits

Insufficient hydration, stress, lack of sleep, or an unbalanced diet can also affect your skin quality and promote water loss.

How is TEWL measured?

Insensible water loss can be measured using specific devices used in dermatology or cosmetology, called evaporimeters. These devices assess the amount of water evaporating from the skin surface over a given period. This measurement is especially useful in clinical studies to test the effectiveness of cosmetic products or to evaluate the skin barrier condition in patients.

 

In daily life, even without devices, some signs can suggest high TEWL: tightness, dull skin, roughness, discomfort, or increased sensitivity.

TEWL and hydration: what’s the difference?

It is important not to confuse skin hydration and TEWL. Skin can lack water (dehydration) while having a relatively intact skin barrier, or conversely be well hydrated but have excessive water loss:

• TEWL concerns the skin’s ability to retain water;
• Hydration depends on the amount of water present in the tissues.

The two concepts are related but distinct.

 

An effective skincare routine must therefore address both aspects:

• Provide water to the skin (moisturizers like glycerin or hyaluronic acid)
• Strengthen the skin barrier to limit losses (lipids, ceramides)

How to limit insensible water loss?

Reducing TEWL mainly involves strengthening the skin barrier. 

Tip #1: choose suitable skincare

Favor gentle products, free of irritating agents, and rich in lipids. Creams containing vegetable oils, shea butter, squalane, or hyaluronic acid are your best allies!

Tip #2: avoid harsh cleansing

Soaps that are too alkaline can damage the hydrolipidic film. Choose formulas that respect the skin's pH.

 

Here, you can turn to the Grangettes Switzerland purifying gel: it contains hydrolyzed wheat protein and cocoyl proline, which ensure optimal skin hydration.

Tip #3: hydrate regularly

Applying a moisturizing cream morning and evening helps maintain a good hydration level and limit water evaporation.

 

For the face, choose a cream rich in hyaluronic acid: the Grangettes Switzerland anti-aging cream contains hydrolyzed hyaluronic acid, olive-derived squalane, and allantoin from comfrey. These ingredients provide intense and lasting hydration: a must-have to restore softness, suppleness, and natural radiance.

 

And for the body? The Grangettes regenerating body milk is your key ally: its expert formula maintains skin structure and regulates its hydration.

Tip #4: use an eye contour gel

The eye contour area is extremely thin and fragile (up to 4 times thinner than the rest of the face). As a result, it loses water more easily, so TEWL is often higher there.

 

A well-formulated eye contour treatment (gel or cream) can:

• Strengthen the skin barrier;
• Limit water evaporation;
• Improve comfort (less tightness, dehydration fine lines).

How to care for this area of the face? The Grangettes Switzerland eye contour gel is your best ally: enriched with hyaluronic acid, it strengthens the upper layers of your epidermis and supports your lipid barrier.

Tip #5: protect your skin from aggressions

In winter, remember to protect your skin from cold and wind. And in summer, use sun protection to avoid UV-related damage, which can also impair the skin barrier!