Dry and very dry skin: what is it and what causes it?

The problem of dry and xerotic skin can be attributed to various factors, which sometimes coexist.

Water is the main component of skin, and a proper level of hydration is a prerequisite for healthy skin.

In fact, dry skin is less resistant and easily irritated, in addition to being more susceptible to inflammation and annoyances such as itching.

The medical term xerosis cutis, from the Greek word kseròs (dry), is often used to indicate very dry and parched skin.

Xerotic skin is rough and cracked and may also experience peeling, tears and fissures. It is also often characterised by itching and redness.

The outermost layer of the epidermis — the stratum corneum — acts as a protective barrier in both directions! It not only protects against external aggressors, but also against water loss from the deeper layers.

The stratum corneum can be compared to a wall in which the cells — the corneocytes — act as bricks, while the cement is represented by lipids (ceramides, cholesterol, fatty acids) arranged in a liquid crystal structure. The surface also features the hydrolipidic film, a mixture of watery and lipid substances formed thanks to the secretion of sweat and sebum.

The result is a sort of wall, but rather than being a simple, static structure, it is complex and dynamic because:

• it is constantly being renewed, like all the epidermis;
• it is constantly alert to everything that happens on the outside and inside;
• it acts non-stop to organise and mobilise water. 

Under “normal” conditions, the stratum corneum acts as an effective barrier, defending against physical and chemical agents as well as pathogenic bacteria; all while regulating the balance of water between the outer environment and the underlying layers of skin. A certain amount of water loss through the skin is natural; this loss is measured as the quantity of water vapour which passes from the stratum corneum outwards: TEWL, or Transepidermal Water Loss.

Low TEWL levels indicate good skin barrier integrity, while high levels are an indicator that the skin barrier has less protective power.

In the event of alterations to the proteins of the corneal cells (the bricks), the inter-corneocyte lipids (the cement), or the hydrolipidic film, the barrier function may be impaired. As a result, the water content of the epidermis is reduced and the skin becomes dry and xerotic.

A dry epidermis may be an “intrinsic” condition because of fragile, ageing, or atopic skin; or it may be an acquired condition caused by external factors such as exposure to the sun, cold and harsh weather, excessive washing or contact with aggressive substances.  

In fact, the problem of dry and xerotic skin can be attributed to various factors, which sometimes coexist:

• Constitutional factors: aside from the question of genetic predisposition, dry skin often affects children or elderly people, as the sebaceous glands of people in these age brackets are less active or inactive.
• Environmental factors: exposure to the sun, wind, heat or cold, using harsh cleansers, mechanical irritation (friction) or wearing synthetic clothing.
• Iatrogenic factors: certain drugs or treatments can cause skin dryness, including severe cases.
• Professional factors: contact with solvents and chemical substances, working constantly in outdoor environments, or professions that involve frequent contact with water (e.g. baristas, healthcare workers, etc.).  
• Dermatological conditions: xerosis is a clinical symptom of certain forms of dermatitis, characterised by abnormal desquamation, skin thickening — hyperkeratosis — or skin irritation, such as ichthyosis, psoriasis and atopic dermatitis, for example.

Dry skin is a fairly common condition. It often affects the parts of the body which are most exposed, i.e. the face and hands, but can occur anywhere.

When treating dry and very dry skin, it helps to adopt habits which, on the one hand, prevent further drying — such as using gentle cleansers — and which favour the skin’s natural hydration mechanisms on the other hand — such as the daily application of hydrating cosmetics.

These moisturisers may have different features: they usually have a more emollient effect if they are to be used on the body, while those intended for use on the face are suitable as a base for make-up and to protect against daily oxidative stress. 

To find out more, read our articles:

Atopic Dermatitis, what it is and how to treat it