How can I determine if my skin is dehydrated?

The skin is an organ made up of three layers: the epidermis, the dermis, and the hypodermis. It contains approximately 30% of the body's total water. This water is unevenly distributed within the skin. Indeed, the dermis concentrates about 80% of it, while the stratum corneum, the outermost layer, only contains about 10%. However, it is in this layer that the lack of water is most visibly manifested on the surface.

The hydration of the skin relies on several intrinsically linked mechanisms: the natural hydration factors, a set of hygroscopic molecules, retain water in the corneocytes, the lipid barrier of the horny layer limits insensible water loss, the aquaporins, transmembrane proteins, ensure its transport between cells, while the hyaluronic acid acts like a true biological sponge at the dermis level. When one or other of these factors is disrupted, the skin loses its ability to retain water and becomes dehydrated.

A well-hydrated skin functions better at all levels: it regenerates more quickly, resists external aggressions more effectively, and exhibits a smoother and brighter appearance.

Skin dehydration results from a temporary imbalance within the hydrolipidic barrier, which no longer effectively retains water. This phenomenon is linked to an alteration of the horny layer: intercellular lipids become depleted, tight junctions loosen, and water evaporates more quickly. Environmental factors, such as cold, dry wind, pollution, prolonged exposure to sunlight, the intake of certain medications, like the isotretinoin, as well as skin ageing can also exacerbate skin dehydration, or even cause it. Several symptoms, visible or felt, allow for the identification of dehydrated skin.

• A loss of radiance and a dull complexion.

  When the skin lacks water, the cells of the stratum corneum can lose the regularity of their alignment and the skin surface can become less uniform and smooth. It then reflects light less effectively, resulting in a loss of brightness. This is indeed why it can be difficult to differentiate between a dehydrated skin and a dull complexion.

• Feelings of tightness, particularly after cleansing.

  Water helps to maintain the flexibility of cellular membranes and ensures good cohesion of the surface layers. When hydration decreases, the skin becomes more rigid, resulting in a feeling of discomfort or tightness, particularly after showering or using harsh cleansing products.

• Visible dehydration fine lines are more noticeable.

  A lack of water in the epidermis reduces the volume of keratinocytes, which accentuates the skin's micro-reliefs. These fine lines, often temporary, appear primarily around the eyes, on the cheeks or the forehead. They are distinct from deep wrinkles associated with the loss of dermal structure, more specifically due to the decrease in the quantity of collagen and elastin, the structural proteins of the extracellular matrix.

• Flakes and small dead skin cells.

  Contrary to what one might initially think, skin hydration and desquamation are correlated. When skin hydration is insufficient, the stratum corneum becomes more rigid and the detachment of dead cells no longer occurs uniformly. This creates visible fluff on the skin's surface, particularly noticeable during the application of facial products.

• A compensatory overproduction of sebum.

  In response to dehydration, certain skin types, particularly combination to oily skin, tend to increase their sebum production in an attempt to restore the skin barrier and the hydration it provides. This defence mechanism can then exacerbate the issues already faced by oily skin, such as shiny areas, blackheads, and blemishes in general.

• An increased sensitivity.

  Finally, by altering the skin's barrier function, a lack of water increases the skin's permeability to external irritants and allergens. The skin can then become more sensitive, more reactive, and more prone to redness and tingling sensations.

A straightforward method to determine if your skin is dehydrated: gently pinch the skin on your cheek. If fine lines appear or if the skin takes time to return to its original shape, it's an indication that it lacks water.

Advice : If your skin is dehydrated, it may be wise to temporarily adapt your skin care routine and focus on restoring the integrity of your skin barrier. We particularly recommend using a gentle cleanser, free from harsh sulfates and formulated at the skin's physiological pH, a hydrating serum, containing active ingredients with hygroscopic and humectant properties, and a moisturising cream suitable for your skin type to seal in hydration.

• BURCH G. E. & al. Differential roles of layers of human epigastric skin on diffusion rate of water. JAMA (2004).

• BONTÉ F. & al. Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology (2007).

• GRANT-KELS J. M. & al. Nutrition and Water. Clinics in Dermatology (2021).

• EL-CHAMI C. & al. Organic osmolytes increase expression of specific tight junction proteins in skin and alter barrier function in keratinocytes. British Journal of Dermatology (2021).

• EDA N. & al. Changes in the skin characteristics associated with dehydration and rehydration. European Journal of Sport Science (2023).