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 directly affects the hydrolipidic film, a protective veil located on the surface of the epidermis 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. In 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 characterized by a lack of water in the superficial layers of the epidermis, particularly at the level of 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, due to the repeated use of an inappropriate 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 characterized 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 glycerin or hyaluronic acid, while strengthening the skin barrier with lipid-replenishing active ingredients.

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

It can sometimes seem challenging to distinguish between dry skin and dehydrated skin, but certain signs can provide clarity. The main factor to consider is the frequency of discomfort experienced. Dry skin often presents 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 important to remember that skin dehydration can affect all skin types, including oily or combination skin: an excess of sebum can 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 seems to lack elasticity overall, it is likely dry.