Did you know that you lose between 300 and 400 milliliters of water through your skin every day, regardless of perspiration? This natural physiological phenomenon has a name: transepidermal water loss or TEWL. It's completely normal, and it plays a key role in the balance and health of your epidermis.
The problem arises when this loss intensifies. The skin then dehydrates faster than it can regenerate and shows signs of tightness, persistent discomfort, dullness, or even superficial fine lines. Understanding this mechanism allows you to adopt the right habits to sustainably maintain skin hydration.
What is transepidermal water loss?
Transepidermal water loss corresponds to the evaporation of water contained in the deep layers of the epidermis and dermis. Water gradually rises to the skin's surface, then naturally evaporates through the stratum corneum, without the intervention of sweat glands.
Unlike active perspiration, this water loss is invisible, independent of thermal regulation, and occurs continuously within your body, even at rest.
You thus lose a certain amount of water each day through this phenomenon, depending on your body surface area, climate, and skin type. This quantity can easily double, or even triple, when the skin's barrier function is impaired.
The stratum corneum, composed of corneocytes, acts as a protective shield thanks to its intercellular lipids such as ceramides, cholesterol, and free fatty acids. When this structure is damaged, water escapes more quickly and leads to progressive skin dehydration.
Why does skin lose water?
Internal causes
Skin aging is one of the most common causes. With age, your skin gradually produces fewer lipids and natural moisturizing factors (amino acids, urea, lactic acid). This decrease weakens the skin barrier and makes the stratum corneum more permeable.
Certain dermatological conditions, such as atopic dermatitis, eczema, or psoriasis, significantly amplify this phenomenon. Published works in the Journal of Clinical Medicine demonstrate that these conditions deeply alter the skin structure and cause significantly higher than normal water loss.
Important: In case of skin conditions (eczema, psoriasis, dermatitis) or persistent symptoms, consult a dermatologist or qualified health professional.
Recent research published in Scientific Reports also shows that hormonal variations during menopause can alter the composition of the hydrolipidic film and accentuate dehydration.
Your genetic heritage also influences the quality of your skin barrier: some people naturally have less effective protection.
External causes
The environment significantly influences TEWL. Dry air, whether from heating in winter or air conditioning in summer, promotes the evaporation of skin water. Cold, wind, and UV radiation weaken the lipid substances that protect your skin. Air pollution aggravates this phenomenon by damaging essential epidermal lipids for the cohesion of the stratum corneum.
Your daily skincare routine is also a factor not to be overlooked. According to scientific observations reported in Acta Dermato-Venereologica, alkaline soaps and overly aggressive products gradually weaken the natural hydrolipidic film. Similarly, excessive cleansing or too frequent mechanical exfoliation ends up weakening the epidermis and promoting skin imbalance.
What are the signs of excessive transepidermal water loss?
The first symptom of excessive TEWL is a feeling of tightness. Your skin lacks suppleness and feels rough. Your complexion becomes dull and loses its natural radiance.
Dehydration fine lines appear, especially around the eyes. Unlike expression lines, they remain superficial and can fade with good hydration.
You may observe fine desquamation, redness, or increased sensitivity to ingredients present in certain cosmetic products. Makeup adheres poorly and accentuates texture irregularities. In more pronounced cases, your skin develops a cracked appearance, particularly visible on the legs and arms. These signs indicate progressive skin imbalance.
How to limit transepidermal water loss?
Strengthen the skin barrier
Opt for skincare rich in ceramides, essential lipids that cement cells together. Ideally, choose complete formulations combining ceramides, cholesterol, and fatty acids: this trio effectively reconstitutes the intercellular cement.
Also rely on occlusive emollients and film-forming agents that create a protective film on your skin's surface. Plant butters (shea, cocoa) and rich oils (argan, jojoba) perfectly fulfill this function, not forgetting humectants like hyaluronic acid. The principle is simple: hydrate the skin, then trap the water with lipids.
Adopt good habits
Cleanse gently: use non-stripping products and prefer lukewarm water. Water that is too hot dissolves your skin's protective lipids.
Control ambient humidity: maintain a level between 40 and 60%, especially in winter when heating dries the air.
Protect your skin from climatic aggressions: wind, cold, sun… adapt your protection according to outdoor conditions.
Hydrate from within: drink 1.6 to 2 liters of water per day to support skin hydration.
Take care of your diet: favor foods rich in essential fatty acids (omega-3 and omega-6) such as fatty fish, nuts, and vegetable oils.
The star active ingredients
|
Active Ingredient |
Main Action |
Benefits |
|
Hyaluronic Acid |
Absorbs water like a sponge |
Immediate and plumping hydration |
|
Niacinamide (2-5%) |
Stimulates ceramide production |
Strengthens the skin barrier and reduces water loss |
|
Amino Acids, Urea, Lactic Acid |
Retains water in the epidermis and dermis |
Lasting hydration and suppleness |
|
Squalane |
Restores the hydrolipidic film |
Protects against evaporation |
|
Panthenol |
Accelerates cell regeneration |
Repairs and soothes skin |
|
Stimulates repair mechanisms |
Heals and strengthens the dermis and stratum corneum |
Hydration vs. Nutrition: Don't Confuse Them!
Hydration concerns water intake: dehydrated skin lacks water, which causes tightness and superficial fine lines. This condition affects all skin types, even oily skin.
Nutrition refers to lipid intake through appropriate cosmetic care: poorly nourished skin has a lipid deficit that compromises its barrier function. Your skin can therefore be dehydrated without being dry, as is the case with dehydrated oily skin. Always combine hydration and nutrition for optimal effectiveness.
Scientific Focus: Measuring Transepidermal Water Loss (TEWL)
The TEWL (Transepidermal Water Loss) test is used to accurately determine the amount of water that evaporates from your epidermis. An evaporimeter measures the moisture gradient between two sensors placed at different distances from the skin.
The evaporation flux is expressed in grams per square meter per hour (g/m²/h). Normal values are generally between 5 and 15 g/m²/h. When the skin barrier is altered, these values can reach 30 to 100 g/m²/h.
FAQ – Transepidermal Water Loss
What is the difference between perspiration and transepidermal water loss?
Perspiration is an active process controlled by your sweat glands, noticeable during physical exertion. Transepidermal water loss is a passive, continuous, and imperceptible evaporation through your stratum corneum.
Can transepidermal water loss be completely eliminated?
No, this physiological phenomenon is natural and necessary. The goal is to keep this loss within normal values by preserving your skin barrier.
What skincare products best limit skin evaporation?
Creams combining moisturizing active ingredients, restructuring lipids, and occlusive agents: ceramides, niacinamide, hyaluronic acid, humectants, and vegetable oils.
Does transepidermal water loss also affect the scalp?
Yes, your scalp has a skin barrier that is weakened by harsh shampoos and heating tools, leading to dryness and itching.
How do I know if my skin lacks water or lipids?
If it feels tight after cleansing but rebalances with a light cream, it lacks water. If discomfort persists and requires rich textures, it lacks lipids.
Conclusion: Preserving Skin's Hydric Balance
Transepidermal water loss directly influences your skin's comfort. Understanding its mechanisms allows you to adopt a suitable routine. Strengthen the barrier function with targeted active ingredients, respectful actions, and attention to environmental conditions. Your skin will thank you with its renewed resilience and radiance.
Want to take action to preserve your skin's hydration? Discover our tablets formulated to support the skin barrier from within. Rich in electrolytes, they help optimize cellular hydration and strengthen natural protection mechanisms against transepidermal water loss.
Bibliography
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