What it is and values
The pH of the skin is at slightly acidic physiological values, normally between 4.2 and 5.6, with peaks up to neutrality. The amplitude of this interval can be explained on the basis of the many factors capable of influencing skin pH.
These factors will be briefly described below.
Endogenous factors
Endogenous factors that determine the pH of the skin
As mentioned, the skin pH is strongly influenced by a series of endogenous factors that give rise to a certain variability between one individual and another.
First of all, the acidity of the skin's pH is linked to the presence of the hydrolipidic film and to the plurality of biochemical processes that take place in the epidermis. The hydrolysis of skin lipids (sebaceous triglycerides, lipid cement ceramides, phosphoglycerides contained in Odland's bodies) to free fatty acids, undoubtedly represents the main phenomenon responsible for skin acidity, also supported by the presence of lactic acid and the production of urocanic acid starting from histidine obtained from the lysis of filaggrin.
The so-called water mantle also participates in the regulation of skin pH, given by sweat, by the substances dissolved in it (mineral salts, lactic acid, urea, ammonium) and by the loss of water due to the phenomenon of perspiratio insensibilis. It is therefore not surprising that the pH of the skin is also influenced by the degree of sweating of each individual.
Other endogenous factors capable of influencing the pH of the skin are represented by the sex and sebaceous production of each individual: in men the sebaceous secretion is greater than in women and this explains, at least in part, the reason why male skin is record pH values generally lower than that of women, thus resulting more acidic. For the same reason, the skin of the child and the elderly has pH values closer to neutrality.
However, it should be noted that the pH of female skin can also vary according to the phase of the menstrual cycle in which the woman is.
At the same time, the pH of an individual varies according to the resident bacterial flora and according to the body area that is taken into consideration. In fact - as can be seen from the table below - the body regions characterized by greater humidity (such as, for example, the armpits and interdigital spaces of the feet) have higher pH values than other areas of the body.
Exogenous Factors
External factors that influence the skin pH
The pH of the skin does not depend only on factors internal to the individual, but is also affected by various external factors. Among these, we remember:
- External climatic conditions (the pH, in fact, can vary according to the season in which you are located);
- Air pollution;
- Diet;
- Application of topical medications;
- Type of clothing used (the use of clothes that are too tight and / or non-breathable could, in fact, cause alterations in the skin's pH);
- Presence of any pathologies.
Furthermore, the pH of the skin can be strongly influenced by the type of cosmetics and detergents used.
Therefore, in the light of this last statement and for what has been explained in the article so far - when there are no dermatological conditions that justify it - the use of neutral detergents or traditional soaps that in contact with water develop a alkaline pH (necessary for dissolving excess skin fats). However, it should be remembered that the ability to modify the pH of the skin depends not only on the type of detergent used, but also on the time of application and the frequency of use.
Especially irritated and eczematous skin tend to have pH values higher than normal; in these cases, the use of traditional alkaline soaps could make the skin even more susceptible to infections.
Functions
Functions of the pH of the Skin
The pH of the skin contributes to the defense against microorganisms hostile to skin health, without however disturbing the resident microflora. An increase in skin pH can therefore favor, especially in those body regions characterized by maceration or pseudo-anaerobiosis, the development of fungal and / or bacterial infections.
A slightly acidic skin pH also favors the activity of skin enzymes responsible for the renewal and maintenance of some skin components, as well as guarantees the survival of the skin microflora which performs various and useful functions for the organism.
In summary, the maintenance of skin pH plays a fundamental role in what is the barrier function exercised by the skin itself.
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