Senile xerosis: what should we know about this age-related skin dryness?

Senile xerosis is the scientific term for a significant skin dryness associated with the skin ageing process. This term originates from Greek, where "xeros" means "dry" and "osis" refers to a disorder or disease. The dry skin observed in older individuals stems from the deterioration of the skin barrier that occurs over time. Indeed, with age, the skin undergoes structural and functional changes that impair its ability to retain water and protect itself from external aggressions. Several biological mechanisms are involved and help explain the onset of xerosis.

Firstly, we can mention the gradual decrease in the production of epidermal lipids, particularly ceramides, cholesterol, and free fatty acids, which significantly impairs the skin barrier function. Indeed, intercellular lipids are essential for maintaining skin hydration by forming lamellar bilayers in the stratum corneum, the outermost part of the epidermis. Their organisation into ordered structures allows for the trapping of water within the epidermis and limits insensible water loss.

Furthermore, the natural moisturising factor (NMF) sees its concentration decrease with age. As its name suggests, it is essential for skin hydration. Present within the corneocytes of the stratum corneum, the natural moisturising factor is mainly composed of amino acids, their derivatives and other hygroscopic molecules capable of attracting and retaining water. Its decrease accentuates transepidermal water loss (TEWL), a phenomenon further exacerbated by the decrease in sebum production by the sebaceous glands observed during skin ageing. Indeed, a decrease in sebum is accompanied by a weakening of the hydrolipidic film, of which it is an essential element. As a reminder, the hydrolipidic film is a protective veil covering the epidermis that both prevents the penetration of pathogens into the skin and limits the evaporation of water.

Over time, the reduction of lipids in the stratum corneum, the natural moisturising factor, and sebum production weakens the skin barrier, promoting the onset of xerosis.

Senile xerosis can be effectively managed through the use of moisturising and nourishing creams. For optimal effectiveness, it is recommended to choose treatments that contain a combination of humectants, film-forming agents, and emollients, in order to compensate for the lack of lipids and improve the skin's hydration and barrier function. Indeed, scientists agree that a combination of hydrophilic and lipophilic molecules is preferable. A study conducted by MICALI and his team examined the effectiveness of a cream containing, among other things, 10% urea to manage the xerosis of 20 patients aged 65 and over.

A four-level clinical severity score was used to assess skin dryness (0 = normal skin; 1 = mild xerosis; 2 = moderate xerosis; 3 = severe xerosis). Pruritus was also measured using a four-level severity scale (0 = no pruritus; 1 = mild pruritus, 2 = moderate pruritus; 3 = severe pruritus). These parameters were observed at the start of the study and then 7 and 14 days after daily application of the cream. A clear improvement in these two factors and in the participants' xerosis was observed.