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Why do we have dry skin?

Dry skin is a skin type that is characterised by its roughness and tightness. This skin dryness can be innate, exacerbated by certain weather conditions or by ageing. Discover in this article all the causes of dry skin.

Summary
Published February 16, 2024, by Pauline, Head of Scientific Communication — 6 min read

Dry Skin: How to Identify it?

Dry skin lacks hydration and nourishment . More specifically, skin dryness is characterised by an alteration in cellular cohesion, a deficiency in natural moisturising factors (NMF) and a deficiency in the production of fatty substances. In dry skin, the production of sebum by the sebaceous glands is insufficient. This leads to an imbalance of the hydrolipidic film . This is normally located on the surface of the epidermis and contributes to maintaining its hydration, as well as protecting it against external aggressions such as wind, cold or pollution. Finally, the synthesis of ceramides , lipids that play a role as intercellular cement, is reduced in dry skin, which impacts the barrier function of the epidermis.

A dry skin is particularly prone to irritations. This skin type is also recognisable by its roughness, dull appearance, lack of suppleness, tendency to flake, as well as the presence of tightness. In extreme cases, redness, cracks and fissures may appear.

Let's note that the terms "dry skin" and "dehydrated skin" refer to two different conditions. Dry skin is a skin type that lacks lipids, while a dehydrated skin is a skin condition that lacks water.

What are the causes of dry skin?

An insufficient sebum production is the primary cause of skin dryness. It results from both internal and external factors.

  • Hereditary.

    In some individuals, skin dryness is due to a genetic predisposition. Indeed, a mutation on the gene coding for the filaggrin protein is often responsible. This protein is normally expressed in epidermal cells and helps to maintain the skin barrier function.

  • Hormonal fluctuations.

    Sebum production is also influenced by hormonal factors. Thus, it is possible for the skin to become dry during puberty, pregnancy or menopause, periods when significant hormonal variations occur. Indeed, female sex hormones, the oestrogen and progesterone, are closely linked to ageing and skin dryness. Oestrogens notably have the effect of stimulating the synthesis of collagen and elastin by fibroblasts, structural proteins of the epidermis. As for progesterone, it stimulates the production of sebum by the sebaceous glands, which promotes the maintenance of the skin's hydrolipidic film. At menopause for example, the synthesis of oestrogen and progesterone by the ovaries is halted. This causes a decrease in sebum production, and thus a weakening of the hydrolipidic film. The skin is then more exposed to skin dryness.

  • Some skin conditions.

    The psoriasis or eczema can also be responsible for skin dryness. These chronic inflammatory diseases often manifest themselves through the appearance of red patches and skin dryness. The causes of these conditions remain largely unknown, but it appears that the risk factors are primarily of two types: genetic and infectious.

  • The natural ageingprocess.

    The skin's ability to produce sebum decreases with age. Indeed, the activity of the sebaceous glands weakens in our thirties, which compromises the hydrolipidic film. The synthesis of ceramides also begins to decline, impacting the skin barrier. Additionally, the level of hyaluronic acid also gradually decreases, starting as early as our twenties. This molecule plays a key role in skin hydration and is notably capable of retaining up to 1,000 times its weight in water.

  • Some environmental factors.

    External factors can also contribute to skin dryness. Prolonged exposure to the sun or to dry and freezing air during winter can weaken the epidermis. These elements can lead to the degradation of the hydrolipidic film that protects the skin. This film tends to thin out and can no longer perform its function properly.

  • The use of unsuitable products.

    When one has dry skin, it is recommended to favour gentle, nourishing and lipid-replenishing treatments, and to avoid any product containing matifying active ingredients such as zinc or azelaic acid. The use of alcohol derivatives and synthetic fragrances is also discouraged, as these products are drying.

  • Hard water.

    After a shower with hard water, feelings of skin tightness may occur, accompanied by various issues such as irritations, itching, or even the appearance of red patches. The explanation is as follows: the calcium and magnesium ions, which make up the hardness of the water, form microcrystals on the skin, causing the prickling sensations.

Sources

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

  • SCHMELZ M. & al. Skin barrier damage and itch: review of mechanisms, topical management and future directions. Acta Dermatologies-Venereologica (2019).

  • TAKAMORI K. & al. Mechanisms and management of itch in dry skin. Acta Dermatologies-Venereologica (2020).

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