The Definitive Guide to Transepidermal Water Loss (TEWL)

The Definitive Guide to Transepidermal Water Loss

Transepidermal water loss, or TEWL, is an essential concept when considering skin dryness. Although often overlooked, TEWL is one of the main reasons why moisturizing the skin regularly - and with the right products - is a crucial step in keeping skin healthy and hydrated.

What is Transepidermal Water Loss?

Transepidermal water loss occurs when the outermost layer of our skin, the epidermis, loses water to the surrounding air through evaporation. In fact, each day, the skin loses approximately one pint of water through this process.

In a fairly humid environment, water evaporation from the skin is slow, and the body can readily replenish the water lost to the air. However, when water evaporates faster than the body can replace it, the skin becomes dehydrated, which can lead to irritated, rough and/or itchy skin that can crack and cause discomfort.

Dry skin also tends to appear more aged, as fine lines and wrinkles are accentuated. As the skin begins to show signs of dryness, TEWL accelerates even further because the skin's barrier function is further limited.

Key Takeaway: Transepidermal water loss is the evaporation of water from the skin to the surrounding environment and is heightened during environmental extremes (e.g. low humidity and/or low temperatures). This explains why dry skin is more common in the winter) and when the integrity of the skin is compromised (e.g. sunburn, skin conditions, injury, etc.). Suggested Reading: How to Select the Best Moisturizer for Winter

learn how to treat winter itch and dry skin

How Do You Minimize Transepidermal Water Loss?

Optimizing the skin’s moisture levels is vital to skin health and an important element in ensuring a youthful appearance. To achieve proper skin hydration and treat dry skin, internal and external factors must be considered.

We all know that meeting our water intake goals each day is beneficial to the body. Water aids in digestion, regulation of body temperature, transportation of nutrients and much more. While the jury is still out on whether drinking water directly improves skin hydration, we do know that it certainly can't hurt. (Suggested Reading: Does Drinking Water Help Your Skin?) That’s the internal side of the equation.

Ensuring adequate water consumption, however, doesn’t prevent TEWL. If anything, the more water content in the skin, the greater the opportunity for TEWL to occur. Rather, from an external perspective, we must focus on slowing the rate of water loss. To do that, we look to moisturizers and, more specifically, moisturizers that contain three key categories of ingredients:

1. Humectants

humectants attract water into the skin

Among the effective humectants used in moisturizers are propylene glycol, hyaluronic acid and sorbitol - substances that naturally attract water. When used in humid conditions, humectants pull water from the environment to the skin. In dry environments, humectants draw moisture from the deeper layer of skin (the dermis) to the outermost layer (the epidermis). However, all of the extra moisture that humectants bring to the epidermis could easily evaporate. This is where occlusives come in. 

2. Occlusives

occlusives help the skin maintain their water content

Common occlusives include petrolatum, caprylic/capric triglyceride and beeswax. These substances are hydrophobic (repel water) and, as such, create a barrier through which water cannot pass. By applying a moisturizer with quality occlusives to the skin, the skin retains its water content. (With certain occlusives on the skin, the rate of TEWL can decrease by up to 98%!)

3. Emollients

emollients reduce water loss

Emollients include ingredients like isopropyl palmitate, dimethicone and jojoba seed oil. These substances help keep the skin smooth, flexible and lubricated. Emollient constituents found naturally in the skin’s oils, such as lipids and fatty acids, play important roles in the skin’s architecture. In moisturizers, they improve the feel and comfort of the skin while greatly reducing water loss.

Key Takeaway: Humectants, occlusives and emollients are important ingredients found in quality moisturizers. Together, they work to minimize and prevent transepidermal water loss while soothing the skin. According to studies, TEWL can be further reduced by using skin care products that, like Lexli, feature a base of aloe vera instead of water.

Lexli Moisturizers, for all skin types

Additional Tips to Slow Transepidermal Water Loss:

  • TEWL is accelerated when the skin’s barrier function is disrupted. Therefore, the amount of water that comes into contact with the skin should be limited. Water dilutes and washes away skin oils that act as natural occlusives to keep water in the epidermis. High water temperature can also increase water loss, as it opens the skin’s pores, allowing more moisture to evaporate. Shorter, cooler showers and baths are recommended for optimal skin health.
  • Avoid strong soaps. Heavy-duty soaps and cleansers with high pH levels can rapidly diminish the skin's supply of natural oils leaving moisture in the epidermis free to evaporate. Rather, turn to gentle cleansers or glycerin bars.
  • In dry climates or during dry seasons, use a cool-mist humidifier in your home or office. Transepidermal water loss is slower in humid environments.
  • Reapply lotions and moisturizers regularly to ensure that skin stays protected. This is especially important after washing hands or cleansing the face or body.

When it comes to skin care products, ingredients are everything. Like all our products, Lexli moisturizers only use ingredients of the highest quality, including a concentrated base of aloe vera - one of nature’s most powerful humectants. In terms of facial moisturizers:

  • Those with normal-to-dry skin benefit from Lexli Night Moisturizer, which features a high concentration of humectants, occlusives and emollients. Despite the name, this product can be used morning and evening by those with dehydrated or dry skin.
  • Those with normal- to slightly-dry skin, as well as those living in humid climates, will appreciate Lexli's selection of lightweight daytime moisturizers and moisturizing serums, which slow water loss and leave skin feeling comfortable, not greasy.
  • For those whose skin is oily we recommend Daily Moisturizer for Oily Skin, which minimizes transepidermal water loss while mattifying the skin.

Finally, to treat dry skin on face and body, we recommend Lexli Hand & Body Lotion.

TEWL Infographic from

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