Cosmetics should be formulated in order to allow their ingredients to better penetrate the skin tissue. The skin, in fact, is not very permeable due to the presence of the lipidic film and to the thick, keratinized texture of its surface layers. Under a chemical and physical point of view, the stratum corneum may be represented as a multi-layer roof structure, where the cells, which are hardened by the keratin filling, correspond to the briks, and the intercellular lipids correspond to the mortar that holds them together. Both intercellular lipids, organized into lamellar structures, and the keratin inside the corneocytes are in fact the strongest barriers to penetration. The epidermal barrier is more efficient than any other biological barrier we know, and its "quality" is closely linked to the quality of the stratum corneum, which accounts for 90% of its protective efficiency. As a consequence, the whole routine of the continuous process of differentiation and keratinization of the epidermis is to produce a high-quality, multi-layer stratum corneum, that is, not only flexible and resistant, but also capable of constant desquamation to maintain the right thickness. Therefore, the stratum corneum performs its protective function by means of its structure, made up by several strata of dead cells - corneocytes - connected and linked together by a fatty cementing substance. The first layer of corneocytes, directly exposed to the external environment, is also covered with a thin film of water and lipids, generally called the surface lipidic film. Thanks to this structure, the epidermis can resist stress from the environment: temperature and humidity changes, chemical and mechanical aggressions, exposure to sunlight, and so on.
However, due to its lipidic and hydrophobic structure, the stratum corneum is also a very difficult environment for any kind of active ingredients; in fact, for the absorption of most compounds, the stratum corneum acts as the rate-controlling membrane; for lipophilic water-insoluble or hydroliphilic water-soluble compounds, diffusion through the epidermis is the limiting step. Any cosmetic treatment must therefore be aimed at the preservation and consolidation of this indispensible barrier, while also maintaining the activity of the polar molecules found in such a hostile environment. By a systematic analysis of these mechanisms, it was possible create the Mavi Diffusion System used for all the skin care lines. There are factors capable of promoting penetration, such as the ratio between lipophilia and hydrophilia in the carrier cream, or the presence of some active ingredients such as linoleic and gamma-linoleic acids, gelatine-glycine or alpha hydroxy acids, which have been used in Mavi vehicles proving very efficient in the enhancement of skin absorption.