With an increase in age, the characteristics of the skin change, and its capacity to combat external aggressions decreases. According to some authors, this condition is driven by changes in lipids that comprise the stratum corneum [1, 15].

Skin aging can induce epidermal lipids and the formation of free fatty acids (FFA), which, as a vicious circle, can further alter the physiological functions forming part of the skin aging process [16, 17].

A recent study analyzed the change in the composition of fatty acids in the epidermis through the process of intrinsic aging and in vivo UV exposure in human skin. The presence of 11,14,17-eicosatrienoic acid (ETA), polyunsaturated omega-3, was found to be significantly reduced in the skin, with a predominance to intrinsic aging [16, 17].

The increase in the content of ETA in the epidermis of photodamaged skin which has been acutely exposed to UV radiation is associated with the increased expression of human elongase-1 and phosphodiesterase A2, which is calcium independent. Thus, it was shown that ETA prevented the expression of MMP-1 after UV irradiation. Inhibition of the synthesis of ETA using, for example, EPTC (S-ethyl-dipropylthiocarbamate), which inhibits human elongase-1, increased the expression of MMP-1 (promoting degradation of extracellular proteins triggered by UV radiation) and contributed to the photoaging of human skin. Consequently, these results suggest that UV rays increase the levels of ETA as a photo-protective mechanism [1, 15, 16].

Fatty acids have received much attention as permeation enhancers, used to enhance the absorption of drugs and cosmeceuticals through the stratum corneum. Among the fatty acids, linoleic and oleic acids have risen to prominence [16, 17].

Although fatty acids are widely used as absorption promoters, the choice of a perfect fatty acid depends on the active substance to be used, as well as the solvent [1, 16].

The understanding of the aging process involves understanding the changes that occur in molecules and their regeneration capacity. One of the biochemical reactions of this process is the nonenzymatic glycosylation, which is known to discolor and harden foods [1, 15].

Nonenzymatic glycosylation is a reaction of an aldehyde group of glucose with the amino group of a protein, to form a base (a Schiff base). This reaction usually occurs enzymatically; however, in collagen and medium- and long-living proteins, glucose can bind irreversibly without the intervention of enzymes. This spontaneous biochemical aging process contributes to the progressive damage of skin tissue and probably to the malfunction of organs (Fig. 32.1) [18, 19].

The end products of advanced glycation (AGE) damage cells by way of four basic mechanisms:

Since endogenous formation of AGE is a slow process, long-lasting proteins, such as collagen, are the proteins most susceptible to the accumulation of AGE [1].

The glycation process is characterized by intra- and intermolecular cross-links, which reduce the possibility of the AGE being removed by catabolic processes, contributing to its accumulation. In collagen proteins, for example, this process contributes to the stiffness and loss of elasticity of the skin tissue. Systemic medications, researched as anti-glycation substances, are as follows: amino guanidine, acetylsalicylic acid, D3P9195, ALT 946, ALT 711, metformin, and angiotensin II receptor blockers [1, 18, 19].

Functional consequences:

Although none of medications listed above has been approved and accredited with a specific anti-AGE indication, although some anti-glycation substances are already in the preclinical and clinical testing phases [1, 18].

Most topical anti-glycation substances available on the market are intended to block the start of the glycation process, interfering in the connection between the carbonyl group of the aldehyde and the amine. The main disadvantage of this blocking process is the failure/lack of selectivity, which may cause possible interference in certain beneficial processes. Topical anti-glycation cosmeceuticals are as follows: Aldeine, Algisium C, Alistin, Ameliox, Coffee Skin, Dragosine, Trylagen, and Preventhelia [18, 19].

The use of metal ions is considered as the oldest medical text registered (about 1500 BC), namely, the Ebers papyrus of ancient Egypt. As an example, calamine (a natural material containing zinc oxide) was prescribed to treat many diseases of the skin and eyes; green minerals based on copper were used for burns and itching [1, 20, 21].

Metal ions are used as beauty products (pigments, colorants) or for skin protection (blocking ultraviolet rays). In direct contact, they not only affect the skin but may cause dermatitis by irritation or allergies if specific concentrations are exceeded [20, 22, 23].

Bioelectricity is one of the fundamental ways for the cells to communicate with each other. The skin uses these bioelectrical signals to activate the process of repair and healing. With aging, these bioelectrical signals decrease and consequently cause a reduction in the production of collagen and elastin. Research has shown that a solution of mineral ions, containing zinc and copper, combined with water can work as a “battery,” generating an electric current resulting in the inhibition of c-fos (a component of the AP-1), decreased greasiness, increased cellular adhesion, improved skin barrier structure, increased firmness, organization and repair of skin tissue, reduced skin response to stress, promotion of skin homeostasis, and inhibition of inflammation (Table 32.2) [1, 22, 23].

The skin is the largest organ of the human body and provides humans with contact to the environment. Its functions are perception, thermoregulation, secretion and excretion, metabolism, and protection. It is, therefore, a complex organ that aids in the defense against the adverse effects of the external environment. To perform this task, the integument should be in its normal condition, i.e., intact [1, 24–26].

For the skin to be in its proper condition of operation, two basic processes are required: skin cleansing and moisturizing. Cleansing contributes to removing the external debris, natural skin secretions, and microorganisms. Moisturizing, in turn, guarantees the water content of the epidermis and the epidermal barrier [25, 27].

Natural moisturizing factor (NMF), intercellular lipids, and ion pumps are part of the dynamic mechanisms involved in natural hydration [1, 24].

Microdermabrasion is an important process in skin rejuvenation, as it accelerates the process of tissue repair, increasing desquamation of epidermal cells, therefore bringing about cell renewal and elimination of dead skin cells. The reduction of cell cohesion promotes skin softness and facilitates the penetration of antiaging products [1, 25, 29].

Microabrasive agents promote exfoliation, whether physical or chemical, and cell renewal. Silica, microspheres of jojoba, walnut shell powder, and Fiber T1 are physical exfoliants that promote a mechanical exfoliation, facilitating the loss of cell adhesion in the surface stratum corneum. On the other hand, chemical exfoliants decrease the cohesion between the corneocytes by different mechanisms. Good examples are retinoids and hydroxy acids [1, 9, 29].

In addition to these active agents, the pharmaceutical and cosmetic industries have provided new direct microabrasive agents (whose main action is to promote desquamation) and indirect microabrasive agents (which operate in basal keratinocytes or in fibroblasts, thus increasing cell renewal and, secondarily, skin peeling) [1, 29].