Table of Contents
Skin dryness (or xerosis) results from alterations in skin physiology: dehydration and damage to the barrier function are the main reasons. Why this happens is instead a different, complex issue and depends on numerous factors. Furthermore, its clinical aspect can vary from modest to very severe pictures. Dry skin is a frequent phenomenon that refers to a “discomfort” of the skin, especially after cleansing the face and body.
Currently, it is impossible to provide a precise definition as it is based on subjective sensations felt by the individual, and it is precisely for this reason that this annoying picture is generally defined as “tight skin.” In this particular situation, however, it is possible to identify thin skin with a dull and opaque complexion, dry to the touch, prone to irritation and redness, often flaky, and sometimes prone to itching, especially on certain body areas such as the legs.
The desquamation and dehydration of the epidermis can correspond to the expression of some important skin diseases which, however, can affect the whole organism (for example, Atopic Dermatitis, Psoriasis, Eczema, Ichthyosis). The skin’s altered barrier function implies a negative change in its plastic-elastic properties, tactile ability, ability to defend itself from the external environment due to increased permeability, and aesthetic aspect. Furthermore, in the most serious cases, the alteration of the barrier function, with a non-virtuous cycle, can determine more penetration of irritating substances and allergens, resulting in irritation, itching, and inevitable scratching, which worsens the situation over time.
Epidemiology And Evaluation Methods
“Normal” skin dryness is a frequent phenomenon; in fact, it affects about 25-30% of the population; it can already arise in the first years of life or appear directly in adulthood. In particular, xerosis is a more common manifestation in older people, as assessed by various epidemiological studies mainly conducted in nursing homes, with a prevalence ranging from 30% to 75%.
Its clinical evaluation can be performed by visual examination, using, for example, the Overall Dry Skin (ODS) score according to guidelines proposed several years ago by the European Group (EEMCO) for measuring the efficacy of cosmetics and other topical products. Some other instrumental methods support verifying the level of skin desquamation, such as the D-scales and adhesive disks for verifying the number and size of the desquamating corneocytes.
To recognize from a strictly dermo-cosmetological point of view “which type of dryness you belong to” or to demonstrate the real effectiveness of a moisturizing/emollient treatment for dry skin, it would be optimal also to carry out an instrumental evaluation with the aid of specific equipment such as the clock (capable of measuring the water content of the stratum corneum through the capacitance parameter), an evaporimeter (capable of measuring the level of TEWL – TransEpidermal Water Loss) and a pedometer (capable of quantifying the presence of fatty substances through a photometric method).
Xerosis is characterized by the alteration of the so-called “barrier function” of the skin. This fundamental function of the skin can be altered due to two different mechanisms: on the one hand, due to dysfunctions of the keratinization process (acceleration-slowdown of cellular turnover); on the other, due to reduced or absent integrity of the hydrolipidic film of surfaces (altered production of the lipid component or excessive loss of water from the stratum corneum).
For this second parameter, two types of skin dryness are generally identified: one characterized by actual skin dehydration (lack of the aqueous component) and one due to hypolipidemia (lack of the lipid fraction). In some cases, these conditions can both occur simultaneously, thus worsening the symptoms. In particular:
- Dry, dehydrated skin is determined by insufficient water, which can be lacking both in the most superficial levels (stratum corneum) and the deeper ones of the skin (dermis). This is the case of the skin paradox, “dry but shiny skin, “better known as combination skin, or dehydrated but with the normal or excessive presence of sebum.
- Hypolipidemic dry skin: it is caused either by a deficit of sebaceous secretion or by a lack of epidermal lipids, i.e., those fatty substances produced by the cells of the epidermis itself, including the “ceramides.” The low production of epidermal lipids makes the skin more subject to fragility, sensitivity and, above all, it is one of the main causes of the onset of wrinkles and other signs of skin aging, as well as some dermatological pathologies such as Atopic Dermatitis.
- It is important to highlight that in both types of dryness, the main factor that is altered is the surface hydrolipidic film, whose balance is significantly unbalanced.
- The hydrolipidic film is a thin “protective veil” produced by the sebaceous glands, epidermal lipids, and sweat/perspiration, essential for maintaining skin emollience and counteracting the development of pathogens. The regions poorly provided with this protective film will thus have less “natural” emollience, and by retaining a smaller quantity of water, they will have a greater tendency to flake.
- An important consideration regarding the physiological skin barrier is that it forms part of the normal dirt we remove daily with cleansing. However, its incorrect removal deprives the epidermis of its protection and exposes the skin to environmental aggressions and dehydration.
In summary, damage to the hydrolipidic film is the main cause of xerosis: the loss of epidermal intercellular lipids means that water is no longer retained by the outer layers of the corneum, causing dehydration.
Causes And Causes
A combination of several factors often causes dry skin:
- Genetic predisposition: some people have constitutionally dry skin. In other words, their skin, at all ages of their lives, is always characterized by excessive dryness. This mainly occurs because hydration undergoes an alteration determined by one or more factors that characterize it: epidermal lipids, surface hydrolipidic film, natural hydration factors (NMF), stratum corneum, and organic substances (salts, amino acids, hyaluronic acid) are no longer represented correctly.
- Gender: dryness is more easily found in women. Regions such as the front face of the legs, often flaking due to different conditions (such as a lower presence of sebaceous glands), if not properly hydrated through specific cosmetic treatments, take on an unpleasant and unsightly appearance.
- Age: apart from some diseases that can appear in childhood, such as Atopic Dermatitis, it is rare to find dry skin in children. In general, xerosis appears after sexual development, and in women, it worsens over the years and after menopause when the estrogen hormones stop “protecting” the female skin.
- Temperature and humidity: a dry and cold climate is the worst that can happen to those who tend to suffer from dry skin. If the ambient humidity is low, the water will tend to evaporate to respect the osmotic gradient, i.e., it will try to spread where there is less humidity. Skin water content is directly correlated with the environmental humidity rate (only above 60% relative humidity can the skin maintain an adequate water concentration).
Daily environment: when we are in the office, at home or in any closed air-conditioned environment, in the car, or on an airplane, we never worry about environmental humidity, thus running the risk of dehydrating the skin. Among the external environmental factors, on the other hand, sun exposure is the one that, more than others, can considerably damage our skin, also in terms of hydration, as the damage induced by solar radiation is capable of altering its structure and barrier function.
- Incorrect hygiene: Washing is a fundamental act for maintaining correct hygiene, but it is also true that excessive cleansing impoverishes the skin’s defenses. Its action produces the removal of the hydrolipidic film, exposing it directly to the activity of the surfactants generally contained in detergent products. Alongside the action of personal hygiene products, there is the even more “degreasing” action of surfactants contained in household products, which end up causing even more serious damage to the skin (as happens when housewives’ hands develop a real Irritative Contact Dermatitis).
- Diet: a poor diet or diet lacking in essential nutrients dehydrates the skin, which will therefore appear not very toned and thus lose the water and lipid content that keep it healthy. When there is significant dehydration of the body, the skin becomes “wrinkled,” the wrinkles are more evident, and the complexion takes on a dull and grayish appearance.
- Habits: bad habits, such as being too photo-exposed, using lamps or sunbeds, taking too long baths or showers, washing too many times during the day, smoking, etc., are all factors that end up constantly damaging the skin, also substantially increasing its dryness.
It is, therefore, evident that in dry skin, the stratum corneum undergoes dehydration and delipidation phenomena. For this reason, a first approach to restoring the skin barrier, in an attempt to re-establish the physiology of the protective film, is to include lipids compatible with those present in the stratum corneum in topical treatment products.
On the one hand, these ingredients can reintegrate the lipid phase and, at the same time, determine better water retention by the skin and therefore determine its greater indirect hydration. Active ingredients with a soothing, decongestant, and adjuvant action in reducing skin itching help restore a normal condition and prevent further irritation. Equally fundamental is using ingredients with direct moisturizing and hygroscopic action (capable of binding many water molecules) to provide the skin with the deficient aqueous substances it needs.