How to distinguish between dry skin and dehydrated skin?

Dry skin is a skin type, meaning it is influenced by genetics and cannot inherently change. Skin dryness results from a lack of lipids, specifically a deficit in sebum production by the sebaceous glands. This characteristic has a direct effect on the hydrolipidic film, this protective veil located on the surface of the epidermis and composed of a mix of sweat, sebum, and water. When the hydrolipidic film is depleted of lipids, the skin becomes more permeable and allows water to evaporate more easily from the stratum corneum, a phenomenon called insensible water loss.

Besides this low sebum production, dry skin exhibits a lipid deficiency within its own stratum corneum. Indeed, within the stratum corneum, ceramides, cholesterol, and fatty acids normally ensure cohesion between the corneocytes, the cells of the most superficial layer of the epidermis. By doing so, these lipids limit transepidermal water loss as they form a barrier against the evaporation of water present in the deeper layers of the epidermis. The lipid deficiency that dry skin suffers from manifests in various ways: the skin often appears quite thin, rough, uncomfortable, with frequent, even constant, tightness. It may also tend to flake or show redness, especially in case of cold or contact with irritating substances.

A dry skin requires care rich in lipid-replenishing agents, to restore missing lipids and strengthen the skin barrier.

A dehydrated skin is not a skin type, but a transient state of the epidermis, which can affect all skin typologies, including oily skin. It is characterised by a lack of water in the superficial layers of the epidermis, particularly in the horny layer. Skin dehydration is often linked to environmental factors (cold, wind, heating, air conditioning, pollution, UV rays...), lifestyle habits (smoking, alcohol, stress, lack of sleep...), or the use of overly harsh products that weaken the skin barrier.

Having dehydrated skin is thus explained by a temporary alteration of the skin barrier function. When the latter has been damaged, for example following the repeated use of an unsuitable cleanser, the skin can no longer effectively retain the water it contains and the water content of the horny layer then decreases. A reduction in natural hydration factors, such as urea, lactic acid or pyrrolidone carboxylic acid, can also exacerbate skin dehydration. Dehydrated skin is characterised by feelings of tightness, a loss of radiance, more visible dehydration fine lines, particularly around the eyes, and sometimes light flaking.

To restore a good level of hydration, we recommend choosing treatments rich in humectants, such as glycerine or hyaluronic acid, while strengthening the skin barrier with lipid-replenishing active ingredients.

Although the terms are often confused, dry skin and dehydrated skin refer to two distinct skin conditions: the former is a permanent condition linked to genetics, while the latter is transient and reversible, caused by external factors.

It can sometimes seem challenging to distinguish between dry and dehydrated skin, but certain signs can provide clarity. The main factor to consider is the frequency of discomfort felt. Dry skin often experiences continuous tightness, regardless of the time of day or weather conditions. In contrast, dehydrated skin shows more fluctuating signs. The tightness appears mainly after cleansing or following exposure to cold or dry air. Moreover, it's worth noting that skin dehydration can affect all skin types, including oily or combination skin: an excess of sebum can therefore coexist with a lack of water in the epidermis. Conversely, it is also possible to have both dry and dehydrated skin.

Advice : Another simple test can help determine if your skin is dry or dehydrated. After gently pinching the skin on your cheek, observe if it forms fine lines. If so, this suggests dehydration. If the skin appears to lack elasticity overall, it is likely dry.