Oily or seborrheic skin, due to an excessive production of sebum, is particularly evident in the skin areas where the sebaceous glands have greater density and greater size: the face (in its central area: forehead nose, cheeks and chin), the presternal lozenge , the interscapular shower and the scalp. Seborrheic skin is thick, shiny, irritable, with enlarged pores and greyish color, sometimes yellowish or brownish-blackish. The thickening is especially visible at the center of the face, on the nose, in the nasolenous nose furrows, in the presternal and interscapular regions. The forehead, temples and chin are less thick. Shiny skin is more visible on the nose and forehead and is associated with the sensation of greasiness to the touch. The pores (follicular orifices) are particularly dilated on the cheeks, at the tip of the nose and are obstructed by cornea cells and sebum.

It is related to sex and age. It affects both sexes, mostly male and can reach its maximum expression between 18 and 25 years. In men it can occur up to 40 years and decreases slightly up to 70 years after which it is drastically reduced. In women already after age 25 there is a reduction of seborrhea up to menopause after which almost disappears. In most cases there is a clear family imprint that lays down for the existence of a hereditary factor, probably multifactorial, responsible for the predisposition to sick.

The production of sebum in a given cutaneous area is closely linked to the number of sebaceous glands present in this area and its functional activity is controlled by several factors: hormonal, stress and diet. The sebaceous gland is under the influence of hormones: some stimulate sebogenesis and others inhibit it. Male sex hormones and ACTH stimulate sebogenesis, thyroid hormones decrease its secretion. The role played by emotional stress and nervous tension on the functions of the sebaceous gland is not yet known. A control by the nervous system is justified by the fact that some neurological diseases such as Parkinson’s disease, epilepsy, encephalitis, severe manic forms can have intense seborrhea. Another controversial topic is the dietary factor ; in fact there is no experimental evidence that the diet can affect sebum production.

Furthermore, the sebaceous gland has a high glycogen content, so it appears to be biochemically autonomous. At the same time, however, alcoholism and obesity can cause hormonal imbalances and indirectly influence sebum activity.
Oily skin can be associated with acne by presenting its typical inflammatory lesions (papules, pustules, nodules and cysts) and non-inflammatory (seborrhea and comedones).

Oily skin is one of the most frequent and difficult cosmetic problems to treat because it is easily irritable and complicates with acne lesions. Moreover, the use of unsuitable cosmetic products can cause an inflammatory process that leads to a particular form of oily skin, the so-called “falsely dry” skin, characterized by the presence of thick skin with dilated pores associated with a desquamation such to give impression of dry skin. This type of skin is frequently found in young women.

A purifying product for oily skin in its formulation must have at least one of these active ingredients: a sebum-regulator, a bacterial lipase inhibitor, a keratolytic agent and an anti-inflammatory agent, so that when applied to the skin, it is able to perform at least one of the following actions: inhibit or regulate the production of sebum, inhibit or treat oily skin, prevent or inhibit the development of acne, and treat acne when present.