What Is Transepidermal Water Loss? A Guide to TEWL and Skin Hydration
By Hollyberry Cosmetics
Transepidermal water loss, or TEWL, is the water that passes through your skin and evaporates into the surrounding air. It happens naturally. Your skin’s outer barrier helps regulate this process, keeping water loss under control.
If your skin often feels tight after cleansing or dry despite using a hydrating serum, it is worth looking at your whole routine. Adding hydration and helping your skin retain it are related jobs, but they are not identical.
Here is what TEWL means, how moisturisers help and where hyaluronic acid fits in.
How Does Your Skin Hold Onto Water?
The outermost layer of your skin is called the stratum corneum. Its structure is often compared to a brick wall: skin cells form the bricks, while the surrounding lipids help hold the barrier together.
This barrier regulates water moving out of the skin and helps protect against substances entering from outside. When its function is disrupted, moisture retention can suffer.
The aim of skincare is to support this natural barrier—not to stop every trace of water loss.
Is TEWL the Same as Dehydrated Skin?
They describe different things:
| Term | What it describes |
|---|---|
| Transepidermal water loss | Water passing through the skin and escaping into the air |
| Skin hydration | The amount of water held in the skin |
| Skin barrier function | How effectively the skin regulates water loss and protects against external substances |
These are connected, but a tight or flaky complexion does not tell you your TEWL level. Symptoms alone cannot establish exactly what is happening within your skin barrier.
For a closer look at common skincare terminology, read Dehydrated vs Dry Skin.
What Can Leave Skin Feeling Dry and Uncomfortable?
Everyday habits and surroundings can make dryness worse. Long, hot showers, irritating cleansers, rubbing the skin and dry indoor air are useful places to start when reviewing your routine.
Dermatologists recommend shorter showers with warm water, gentle cleansing and applying moisturiser promptly afterwards. A humidifier may also help in a dry room, provided it is cleaned regularly.
Skin conditions can also affect water retention. For example, eczema disrupts the skin barrier, allowing water to escape more readily. Persistent dry, itchy skin may therefore need more than a change of serum.
Which Skincare Ingredients Help?
Moisturisers often combine several ingredient types. You do not need a separate product for every category.
| Ingredient type | Main role | Examples |
|---|---|---|
| Humectants | Attract and retain water | Glycerin, urea |
| Emollients | Soften and smooth rough skin | Glyceryl stearate, lanolin |
| Occlusives | Form a surface layer that reduces evaporation | Petrolatum, mineral oil, dimethicone |
One cream can provide hydration, softness and protection against water loss. The finished formula matters more than finding a single fashionable ingredient.
Do you need a thick ointment?
Not everyone does. Ointments are generally more occlusive than creams and can suit particularly dry, scaly areas. Creams offer a lighter option for broader use.
Choose a texture that meets your needs and feels comfortable enough to use consistently.
Where Does Hyaluronic Acid Fit In?
Hyaluronic acid is a hydrating ingredient found in skincare products. It can be part of a routine for dry skin, alongside a suitable moisturiser.
Hollyberry’s Hyaluronic Acid Serum contains three ingredients:
- Aqua
- 1% hyaluronic acid
- Phenoxyethanol
It is also perfume-free.
Think of the serum as a hydration step. If your skin still feels dry afterwards, consider the moisturiser you apply over it rather than automatically adding more serum.
A simple water-based serum does not provide the same blend of emollient and occlusive ingredients as a richer cream. Moisturisers containing those ingredients can help reduce evaporative water loss.
For application advice, see How to Properly Apply Hyaluronic Acid Serum.
A Simple Routine to Support Moisture Retention
1. Cleanse gently
Use warm water and a gentle cleanser. Avoid scrubbing, and pat your skin dry instead of rubbing it.
2. Add a hydrating serum if you want one
Follow the serum’s directions. This is an optional step: you can build an effective basic routine around cleanser, moisturiser and sunscreen.
3. Apply moisturiser promptly
Apply your moisturiser while your skin is still slightly damp. Reapply when needed, particularly after washing.
4. Protect your skin during the day
Use broad-spectrum, water-resistant sunscreen with SPF 30 or higher, alongside shade and protective clothing.
Practical tip: If you are changing your routine, make one change at a time. That makes it easier to judge which product improves comfort and which causes problems.
What If You Have Oily Skin?
Choose your moisturiser according to how your skin feels and the texture you prefer. A lightweight gel may suit oily skin, while a cream may be more comfortable for dry skin.
If you are prone to blocked pores, look for a product labelled non-comedogenic. You do not have to use the heaviest moisturiser available to include a moisturising step.
Our guide to Hyaluronic Acid for Oily Skin explores how to choose a comfortable routine.
When Should You Seek Advice?
Seek advice if dryness becomes painful, cracked, bleeding or persistently irritating, or if a gentle routine is not helping. A dermatologist can assess whether a skin condition or a reaction to a product needs treatment.
Avoid assuming that every episode of stinging or flaking is simply “dehydration” that needs another serum.
Frequently Asked Questions
Is transepidermal water loss bad?
TEWL is a normal process. The concern is excessive water loss associated with poor barrier function, rather than water leaving the skin at all.
Do I need a serum and a moisturiser?
No. A moisturiser can contain hydrating, softening and occlusive ingredients within one formula. A serum is an optional addition based on your preferences and skin needs.
Should moisturiser go onto damp skin?
Yes—applying moisturiser to slightly damp skin after washing helps retain water. Follow any separate instructions supplied with prescription treatments.
Does dry skin always mean eczema?
No. Dryness has several possible causes. However, eczema can affect the barrier and increase water loss, so recurring itchy patches deserve attention rather than repeated product changes.
Choosing Your Hydration Routine
Start by reviewing your cleanser and moisturiser. If you would like an additional hydration step, explore Hollyberry’s Hyaluronic Acid Serum and follow its application directions.
Keep the routine manageable, choose products your skin tolerates and assess comfort alongside appearance.