We’ve all dealt with skin dryness at some point and come across terms like skin barrier. Well, transepidermal water loss (TEWL) is the missing piece of this whole puzzle that ties everything together. Because TEWL is closely related to skin hydration, and skin barrier function. So if you’re dealing with dryness and you’re not exactly sure what’s going on with your skin, understanding TEWL can help you pinpoint the problem and map out the way to remedy the situation. Keep reading to learn about transepidermal water loss in skincare, what causes it, and how to treat and prevent it.
What Is Transepidermal Water Loss?
Transepidermal water loss, or TEWL, is the amount of water evaporating from the skin into the air at a given time under normal circumstances excluding sweat (1).
Transepidermal water loss is a natural process that happens every day on our skin. It’s expected. So TEWL itself is not something bad.
It’s an increase in TEWL that requires intervention. Excessive TEWL can result in dry skin symptoms, skin dehydration, dullness, and tightness.
The level of transepidermal water loss varies in different areas of the skin. For example, TEWL is higher on facial skin than it is on the body.
The average transepidermal water loss is 300-400/ml a day (2). TEWL happens throughout the day but peaks in the evening and at night (3).
And in case you’re wondering, transepidermal water loss is measured by a device called Tewameter, which isn’t something accessible for regular people like us.
While simpler versions are available for at-home use or the ones you see at the beauty counter offering a free skin analysis, the results won’t be nearly as accurate as the measurement itself is pretty sensitive (4).
Even the ones in a professional setting are sensitive to air, humidity, the temperature of the skin site being measured, and so on. So basically, you can’t measure your own transepidermal water loss at home.
What Is The Importance of TEWL in Skincare?
TEWL is important because it’s the most objective measuring tool that assesses the function of the skin barrier and overall skin health.
For example, an increase in transepidermal water loss indicates a compromised skin barrier (5). A compromised skin barrier leads to excessive TEWL.
As you can see, transepidermal water loss and skin barrier function go hand in hand. This means that TEWL can work like a mirror to help you understand what’s going on beneath the skin.
For example, if you have high levels of TEWL, you might want to take a look at the products you use. It can tell you whether your moisturizer is enough to sufficiently moisturize your skin, or whether that new exfoliating serum is too much for your skin.
You need to address high TEWL because it has both short-term and long-term effects. High TEWL means that the protective skin barrier is not functioning properly, making your skin susceptible to further skin damage, irritation, inflammation, sunburn, and early signs of aging.
What Causes Transepidermal Water Loss?
Again, transepidermal water loss is a natural process and isn’t something to worry about. However, several factors can increase transepidermal water loss. So what are those factors that exacerbate TEWL?
- Low humidity environment can dehydrate your skin leading to increased TEWL
- High temperatures such as indoor heating can lead to increased TEWL because of dry air
- Skin-irritating surfactants such as sodium lauryl sulfate (SLS) and soaps can dry your skin, and damage the skin barrier, causing excessive transepidermal water loss
- People with skin conditions like rosacea are more susceptible to higher transepidermal water loss, especially during flare-ups
- Pollution can lead to an increase in TEWL because pollution causes free radicals which are harmful to the skin (6)
How To Know If You Have High Levels of TEWL
As we’ve established, you can’t measure your own transepidermal water loss. So then how do you know if you have excessive TEWL? You look at the indications.
High levels of transepidermal water loss result in dry skin, especially in the morning, overall tight-feeling, itchy skin, noticeable fine lines from dehydration, and even sensitivity.
These indicators overlap with signs of an impaired skin barrier because, again, high TEWL is an indicator of an impaired skin barrier.
If you’re dealing with these concerns, you might be experiencing raised transepidermal water loss. But this is manageable. Here’s how you can do it.
How To Stop Transepidermal Water Loss
If you’re experiencing tightness and dryness, here are the best ways to minimize transepidermal water loss and help your skin retain water.
1. Avoid Surfactans in Your Cleansers
Surfactants like SLS and soap are commonly found in daily facial cleansers and face washes. Avoid surfactants and go for SLS-free and soap-free cleansers.
These types of cleansers won’t dehydrate your skin, strip it of natural lipids, or irritate your skin. Considering that we usually wash our faces twice a day, using a gentle cleanser is a good place to start treating TEWL.
As TEWL causes water to evaporate from the outer layer of the skin (stratum corneum), you can replenish the water content of the skin simply by hydrating your skin.
Hydration refers to ingredients like hyaluronic acid and glycerin. Look for these ingredients in your face serums. But this is half the story, which brings me to my next point.
3. Use Occlusive Moisturizers
Occlusive moisturizers form an occlusion on the outer layer of the skin, physically preventing water from evaporating. While it may not be the most pleasant feeling, you can use occlusive moisturizers at least until your skin is recovered.
Occlusive moisturizers are usually thicker and made with ingredients like shea butter, vegetable oil, and coconut oil. Pair your hydrating serums with these types of creams.
4. Invest in a Humidifier
An indoor humidifier increases moisture in the air and prevents skin dryness. Considering that TEWL peaks at night, making this little change can significantly improve your environment and reduce water loss.
5. Avoid Hot Temperature
Hot water both irritates and dehydrates your skin, especially prolonged exposure to water. Try to keep your showers short. If you’re taking a long bath, moisturize your skin and your body right after showering.
Because as soon as you hop out, the skin starts to lose moisture. Using a body lotion and your face moisturizer right after a shower or bath is a great way to prevent transepidermal water loss.
6. Use SPF Regularly
Sunscreen protects the skin from free radicals caused by sun exposure. Free radicals do a number on the skin and cause dryness, dehydration, redness, and of course, wrinkles. To prevent this, remember to use SPF regularly and reapply every 2 hours.
7. Repair Your Skin Barrier
As we’ve established, TEWL happens as a result of an impaired skin barrier. So by repairing your skin barrier, you can slow down and reduce TEWL.
In addition to following the best practices above, follow an intentional skincare routine consistently and be mindful of the products you use.
Use barrier repair creams made with ceramides or niacinamide. Avoid any physical damage to your skin by using scrubs and physical exfoliators. Reduce the frequency of your retinol use.
And as TEWL peaks at night, invest in a good nighttime skincare routine. There’s a reason why night creams are usually thicker than day creams.
So take the time to wash off with a gentle cleanser, use hydrating toner and serum, and apply an occlusive night cream to stop unnecessary transepidermal water loss at night.
8. Don’t Forget Your Hands
Our hands are the most susceptible to surfactants because of frequent hand washing. So don’t stop with your face and include your hands and your whole body.
Moisturize right after exposure to water and reapply moisturizer as frequently as necessary. Remember, TEWL is not exclusive to your facial skin.
So this is what transepidermal water loss is, what it means for your skin’s health, and how you can minimize it. As someone with rosacea, my skin is inherently sensitive, inflamed, and prone to dryness. I’ve learned to read the signs of increased TEWL and to quickly take a break from exfoliants and focus on strengthening my skin barrier. And you don’t know how much of a difference it makes until you see how your skin looks when it’s sufficiently moisturized with a strong skin barrier. So don’t neglect skin dryness and follow these steps to reduce TEWL and help your skin get back on track.
- Draelos, Z. D. (2015). Section 1: Basic concepts: Transepidermal water loss [E-book]. In Cosmetic Dermatology: Products and Procedures (2nd ed., pp. 30–31). Wiley-Blackwell. https://doi.org/10.1002/9781119676881.ch19
- Honari, G., & Maibach, H. (Eds.). (2014). Chapter 1 – skin structure and function. In Applied Dermatotoxicology (p. 1-10). Academic Press. https://doi.org/10.1016/B978-0-12-420130-9.00001-3
- Yosipovitch, G., Xiong, G. L., Haus, E., Sackett-Lundeen, L., Ashkenazi, I. E., & Maibach, H. I. (1998). Time-Dependent Variations of the Skin Barrier Function in Humans: Transepidermal Water Loss, Stratum Corneum Hydration, Skin Surface pH, and Skin Temperature. Journal of Investigative Dermatology, 110(1), 20–23. https://doi.org/10.1046/j.1523-1747.1998.00069.x
- Alexander, H., Brown, S., Danby, S., & Flohr, C. (2018). Research Techniques Made Simple: Transepidermal Water Loss Measurement as a Research Tool. The Journal of investigative dermatology, 138(11), 2295–2300.e1. https://doi.org/10.1016/j.jid.2018.09.001
- Barel, A.O., Paye, M., & Maibach, H.I. (Eds.). (2010). Handbook of Cosmetic Science and Technology (3rd ed.). CRC Press. https://doi.org/10.1201/b15273
- Green, M., Kashetsky, N., Feschuk, A., & Maibach, H. I. (2022). Transepidermal water loss (TEWL): Environment and pollution-A systematic review. Skin health and disease, 2(2), e104. https://doi.org/10.1002/ski2.104