What is Skin Dehydration?
One of the skin’s most important functions is water conservation, acting as a semi-permeable barrier to the loss of water. The skin’s epidermal and dermal layers have different functions, but water conservation depends on both.
The stratum corneum functions as a semi-permeable barrier, allowing the body to survive in a hostile environment. The dermis is the supporting layer, forming a matrix that provides shape and form to the skin through its sponge-like aperture of water, collagen, elastin, and other substances.
The dermis also contains blood vessels that provide the epidermis and dermis with water and nutrients to regulate skin temperature, lymph for the removal of toxins, nerves, and more.
Preserving a youthful appearance requires an ideal hydration balance deep within the epidermis and dermis to prevent excessive transepidermal water loss. Maintaining this level of moisture requires a well- structured epidermis that is fully capable of its role as a protective barrier.
What is TEWL?
Water moves through the body and serves its internal needs, then moves to the surface of the skin in a process called, “transepidermal water loss” (TEWL). Well-balanced skin maintains a healthy TEWL, leaving skin pleasingly plump and firm, and well hydrated. Water comprises up to 75% of the skin’s overall weight, but only 10-15% of the stratum corneum. If the body lacks adequate water, the skin’s outer layers become dry and brittle. If the water content of the epidermis falls below 10%, it becomes dry, less flexible, and increasingly prone to damage, breakdown, and infection.
Drinking at least six glasses of water daily and eating fluid-rich fruits and vegetables helps normalize dry or oily conditions, and is essential to the moisture balance in the body and in the skin. The epidermis is about 35 micrometers thick when dry and dehydrated, but can swell to 48 micrometers when fully hydrated. The skin also requires external water replenishment. Topical products such as sodium hyaluronate, sodium PCA, sorbitol, glycerine, and propylene glycol are designed to maintain hydration.
Products that hydrate the skin play a variety of roles. Hydrators and occlusives work with the surface of the skin in a barrier function, sup- plying oils and hydration. Humectants and emollients work within the skin’s layers, attracting and holding water in the cells, depending on their ability to penetrate.
Hydrators impart a temporary barrier to damaged stratum corneum, which allows time for reparation of this layer. This enables surface hydration, treating dry skin that is not necessarily dehydrated. Hydrators of the new millennium include agents that mimic natural ingredients and functions, stimulating hydration and repairing the mantle.
Occlusives (also known as lipid barriers) physically block the surface of the stratum corneum and reduce transepidermal water loss. This increases the water content in the stratum corneum, producing a state of hydration. Occlusion is one of the best treatments for dry skin because 1) transepidermal water is the most effective source of water for the skin, and occlusives prevent excessive water loss, and 2) these occlusive agents have some emollient effect, as below.
Emollients fill the spaces between the corneocytes, the keratinized cells of the stratum corneum, providing therapeutic improvement to desquamation defects. Emollients smooth roughened skin, improve the skin’s appearance, and lubricate and replace natural skin lipids, providing some occlusion.
Humectants are substances that attract and provide water to the skin and then bind it to the cells of the epidermis and dermis. The source of the water for the epidermis is usually transepidermal, from the air and topical products. The source of hydration for the dermis is derived from the functional aspects of the layer, such as the blood and dermal production of glycosaminoglycans and other inherent components, and from topical products designed with sophisticated delivery systems.
Dehydration vs dry skin
Dry skin is not the same thing as dehydrated skin. While they have similar qualities, they have different underlying causes. Dry skin results from inadequate levels of oils (lipids) deposited on the surface from the sebaceous glands, while dehydration results from a lack of water in the skin.
Dry Skin, as a skin type or inherited trait, has small pores and may be stiff or even flaky, causing less oil to be deposited on the surface of the epidermis. Dry skin as a skin condition can occur in any skin type and is caused by irritants such as sun exposure, harsh cleansers, and other factors such as wind and pollution. Dry skin has an easily irritated, possibly flaking surface and seeks surface moisturisation. Dry skin is treated with non-comedogenic oils on the skin surface.
Dehydrated Skin, as a skin condition, has less water than normal skin. This can occur through moisture evaporation, excessive transepidermal water loss, and environmental exposure. Examples of environmental factors include wind, which can pull hydration from the skin, and long showers or other activities characterized by prolonged exposure to water. Over-cleansing, use of certain medications, and application of the wrong skincare products can also cause dehydration. Dehydration can affect any skin type, including skin with either large or small pores. Tiny, crepe-like, triangular fine surface lines that can be seen through the magnifying light indicate dehydrated skin. Correctly assessing the condition of the skin as dry, dehydrated, or both, is important to choosing the right products.