TEWL 101: What Transepidermal Water Loss Is & How to Stop It
If your skin feels tight, flaky or uncomfortable no matter how many hydrating products you apply, the issue may not be dryness alone, it could be transepidermal water loss (TEWL). This invisible process is one of the most overlooked causes of dehydration, skin sensitivity and premature ageing.
Understanding the meaning of TEWL and how it impacts your skin is the first step towards lasting hydration. At its core, the solution lies in strengthening your skin barrier. Because when your barrier is compromised, moisture escapes faster than your skin can replenish it.
What Is Transepidermal Water Loss (TEWL)?
Transepidermal water loss refers to the natural process of water evaporating from the skin into the environment.
This occurs continuously, even when your skin feels balanced. However, when the skin barrier is weakened, water loss in skin accelerates, leading to dehydration, irritation and visible signs of ageing.
Before we go any further, though, it's important to distinguish between dry and dehydrated skin.
Dry skin (a skin type) lacks oil Dehydrated skin (a skin condition) lacks water
TEWL in skin specifically relates to water loss, meaning even those with oily skin can experience dehydration if their barrier is compromised.
Another important factor: TEWL is naturally worse at night. While you sleep, your skin temperature rises, making your moisture barrier less efficient and more permeable, resulting in your skin losing more water. This makes overnight barrier repair essential for maintaining hydration balance.
What Causes Transepidermal Water Loss & What Are the Signs?
So, what causes transepidermal water loss to spike? Several internal and external factors can weaken the skin barrier:
Environmental Stressors
Cold air, wind, UV exposure and pollution all strip the skin of moisture and disrupt its protective barrier.
Over-Cleansing & Over-Exfoliation
Harsh cleansers and excessive exfoliation can break down the lipid layer, increasing TEWL.
Ageing & Lipid Decline
As skin matures, it produces fewer natural lipids like ceramides and fatty acids, making it harder to retain moisture.
Inflammation
Chronic irritation weakens barrier function, allowing more water loss in skin and reducing resilience.
Now, when your TEWL skincare concerns go unaddressed, your skin begins to show it. Common signs include:
- Tightness immediately after cleansing
- Flaking or rough texture despite moisturising
- Makeup settling into fine lines
- Increased redness or sensitivity
These symptoms often indicate that your skin isn't retaining hydration effectively, even if you're applying hydrating products.
Why TEWL Accelerates Skin Ageing
Uncontrolled transepidermal water loss doesn't just cause temporary dehydration; it contributes to the look of long-term skin ageing. That's because when moisture escapes too quickly:
- Fine lines and wrinkles become more pronounced
- Skin texture appears rough and uneven
- Elasticity and firmness decline
- Redness and irritation increase
A compromised barrier leaves skin vulnerable to environmental damage, creating a vicious cycle where TEWL in skin continues to worsen over time. In other words, hydration isn't just about comfort; it's essential for maintaining youthful-looking skin.
Ingredients That Help Reduce It
The key to minimising TEWL and its ageing effects is using ingredients that attract and seal in moisture while repairing skin's barrier to ensure it doesn't escape. These include:
Humectants
Moisture-binding ingredients like hyaluronic acid, glycerin and osmolytes help draw water into skin and are essential for increasing its moisture content.
Emollients
Softening and soothing emollients like ceramides, squalane and omega fatty acids replenish the lipid layer to help smooth and strengthen the skin barrier.
Occlusives
Moisturising ingredients like shea butter and dimethicone create a protective seal atop the skin to prevent moisture from escaping.
Barrier-Supporting Actives
Advanced ingredients like Neuropeptides, niacinamide and antioxidants help restore and maintain barrier integrity to improve overall skin health and resilience.
Stronger Barrier = More Youthful-Looking Skin
As you can see, maintaining optimal hydration is essential for healthy, youthful-looking skin, and minimising transepidermal water loss is a key part of that process.
Not sure where to begin? Rosalba Martone, Head of Education for Perricone MD, recommends these two essentials:
1. Cold Plasma Plus+ Advanced Hydrating Complex
£95.00
Designed to directly support the skin barrier, the key defence against TEWL. By combining moisture-binding and barrier-reinforcing ingredients, it helps keep hydration locked into the skin throughout the day.
Its Hydra-Osmolyte Blend and hyaluronic-supporting components draw water into the skin, while squalane and omega fatty acids replenish the lipid layer that prevents moisture from escaping. At the same time, niacinamide and copper tripeptide help support barrier function and improve the feel of skin resilience, reducing the likelihood of water loss over time. Neuropeptides further support overall skin health, helping the complexion appear smoother, firmer and more balanced.
Together, these ingredients create a well-hydrated environment that not only minimises water loss but also improves texture, tone and visible signs of ageing.
2. High Potency Intensive Smoothing Serum
Recommended Retail Price: £83.00Current price: £33.20
60% Off
Complements this by refining the skin surface while reinforcing its ability to retain moisture. Niacinamide plays a central role again, helping to support the barrier and reduce water loss while ceramides restore essential lipids that seal hydration into the skin.
Humectants like glycerin and hyaluronic acid attract and hold water within the upper layers, immediately boosting hydration levels. Dimethicone forms a lightweight, breathable seal that further prevents moisture evaporation, and peptides support overall skin integrity. Meanwhile, DMAE contributes to improved firmness, enhancing the skin's structural resilience.
By visibly smoothing rough texture and reinforcing the barrier simultaneously, this serum helps create a softer, more even surface that is better equipped to maintain hydration and resist ongoing TEWL.
Together, these formulas work synergistically to strengthen the skin barrier, enhance moisture retention and visibly improve overall skin health.
