Oily Skin
Whereas dry skin reflects a functional change of different skin components, the oily skin results from an overactivity of the sebaceous glands, leading to an overproduction of sebum overflowing on the skin, giving it a characteristic oily and shiny appearance.
In fact, sebum results from the disintegration of specific cells, the sebocytes, a short time before they are secreted from the sebaceous gland. Once again it results from a cell differentiation. Originally, sebum contains squalene, waxes, triglycerides, and sterols. Under the effect of resident bacteria, one part of the triglycerides is immediately hydrolyzed, and the main part of the cholesterol is esterified, the sebum excreted containing a significant quantity of free fatty acids contributing to the acidity of the pH of the skin surface.
Then this sebum blends with epidermal lipids produced from the destruction of the desquamated horny cells that also contain triglycerides and cholesterol to form the surface lipidic film covering the stratum corneum.
Human beings have the particularity to have at their disposal sebaceous glands almost all over the body, but their activity is not the same on all the anatomical sites. The production of sebum is more important on head, face, neck, shoulders, and thorax, areas where a hyperseborrhea can be the conjunction of a high production of the glands and of a greater number of glands.
Sebum is a natural skin detergent that gives the skin an amphiphilic wettability through the presence of free fatty acids and wax. It also plays a part in the maintenance of the functional qualities of hairs, a fungistatic activity, while having a nutritional function for bacterial species useful for the organism, and finally, a protective function against excessive dehydration in a dry environment through its effect on the epidermal barrier function, even if the sebum is not known to have a dampening activity and has no influence on the skin’s hydration level .
The change of its rate of production depends on genetic, endocrinic, and environmental factors.
The opposite of oily skin would not be dry skin since they can coexist, for example, on face. Such a statement is currently supported by many workers.
Actually, young children fairly never have seborrheic outbreak before the age of seven years, when the first secretion of androgenic precursors starts to form. This production will progress to reach its maximum at adolescence and then decrease with age.
It is also worth noting the racial differences related to sex—men globally having an oilier skin than women. Finally, at cosmetological level, it must be retained that oily skin is sometimes erythrosic, easily irritable, and particularly fragile.