Errors and Trends in Cosmetics
A natural alpha-hydroxyacid for an effective cosmetic treatment
The skin, and, in particular, the epidermis, is one of the most active of tissues, with regard to its restructuring abilities (repair and reorganisation) precisely because it is in direct contact with the external environment, in itself hostile.
Which layer of the skin is responsible for this activity ?
The cells of the basal layer are genetically programmed to become an active factor. They are capable of generating, as required, the amount of keratinocytes necessary to give life to a normal cutaneous surface.
Indefinitely ?
No, not indefinitely. This capacity like all biological ones, depends on a number of conditions: among these, a certain amount are of interest from a cosmetological point of view, in the sense that they can be controlled by adequate cosmetic treatments, w hile others appear after inadequate cosmetic treatments.
Which ones, for example ?
In cases where the skin is no longer sufficiently protected from aggressive external factors by a resistant stratum corneum. This can occur, for example, as a result of long term cosmetic treatments which are in vogue at a given point of time: the use of enzymotoxic surfactants, the use of ingredients intended to reduce perspiration insensibilis, and, the latest trend, peeling through the use of alpha-hydroxyacids (AHA).
What are the consequences of over-doing skin exfoliation ?
Over-doing skin exfoliation, however moderate this may be, causes the cells of the basal layer to sub-divide more rapidly, thus forcing the layers directly above, which receive them, to speed up the stages preparatory to the formation of, in the first place, the definitive keratinocyte, and, in the second, the corneocytes. In this manner, the maturation process, which under normal circumstances is the result of a sequence of different stages (e.g. the production of the cytoskeleton, the synthesis of filaggrin, and the organisation of the keratin), will take place in an incomplete manner in the first instance, and, subsequently, in an ever more erratic and abnormal one.
What from a purely cosmetic point of view ?
To continually provoke artificial skin peeling by accelerating the action spontaneously carried out by the skin itself (physiological desquamation is nothing else than a programmed peeling process) necessarily leads to the formation of incomplete keratinocytes which are unable to evolve into a physiological stratum corneum. This type of treatment does no less than encourage and highlight the tendency to peel which is already far too pronounced (and which is followed by hyperkeratosis) that is becoming mor e and more noticeable in skin still considered as "normal", but which is in fact not normal at all. This type of skin is really, and this can be confirmed, an area where pathological damage of a dys- or hyperkeratosic type is beginning to develop. There is no doubt that this is a surface where negative processes can easily become established, and where mycoses, eczema resulting from various causes, psoriasis, ichthyosis etc. can worsen in terms of both quality and quantity.
Can AHAs enter into the composition of a cosmetic product in any way ?
No. It is a paradox that the cosmetic product can, instead of helping the skin in its physiological expression, disturb its metabolic turnover, thus endorsing its morphological exhaustion, in the first place, and, what is more serious, its functional exhaustion in the second. The use of AHAs does not represent a scientific cosmesis, but rather - and this being the best of hypotheses - aberrant and "easy" cosmesis, which, by offering a modest and all too short-term an improvement, lays down the basis for chronic, insidious and substantial damage.
That goes for any substance which aims to speed up the surface metabolism and which in some way interferes with the skin's enzymatic activities.
Which is the relationship between AHAs activity and pH values ?
There is a direct relationship between their activity and low pH values (these must always be below 5.5 - say, between 3 and 5.5). Consequently, and by definition, activity occurs on an irritative base, while rational cosmetic treatments, opposite to derm atogical ones, should never disturb skin physiology.
Does any natural alpha-hydroxyacid exist which respects skin needs allowing an effective cosmetic treatment ?
Yes, Keresine which contains L-malic acid, an alpha-hydroxy acid, concentrated from cherries (Prunus avium et al. spp.).
L-malic acid, a natural isomer also available in other plants and fruits such as apples and red currant, is a weak, hygroscopic acid belonging to the group of alpha-hydroxy acids. It is a substance which has the ability to draw moisture to the skin’s surface and can thus favourably modify the moisture content and elastici ty of the skin when topically used. 3% malic acid has a relative effectiveness (indicated as therapeutic index, the ratio between cell renewal stimulation and irritant action) appearing acceptable from the consumer point of view and perception (Smith, W.P., 1994). 4% malic acid has a kerato lytic activity of about 40% at pH= 3.5 and 30% at pH= 5.5. Because of its gentle exfoliation effect deriving from the natural intrinsic properties of malic acid combined with a significant buffering level of proteins, high in aspartic acid, which contributes to skin smoothing, Keresine eliminates the skin’s rough upper layers and small imperfections. It is also useful for cosmetic products designed to improve the appearance, complexion and softness of the skin as well as to prevent formation of small wrinkles. Compared to the pH of the other hydroxy acids, which is lower than 3.0, Keresine has a pH (3.3) closer to the pH > 3.5 of a finished cosmetic containing AHA as suggested by regulatory and sanitary authorities. Therefore, the pH value of Keresine is with in the limits correctly controlling the potential irritant effect, thus resulting in skin care benefits including a greater smoothness, moisturization and cohesion of the skin, a more even looking complexion. Applications of only 2% - 5% are useful to obtain:
- skin care emulsions and gels;
- body preparations;
- cleansing lotions and liquids;
- face and neck preparations;
- night skin care formulations;
- masks.