How can I determine whether my skin is combination or oily?

Oily skin is primarily characterized by an excessive production of sebum. Composed of a mixture of various lipids, sebum is secreted by the sebaceous glands and serves to protect and hydrate the skin. Along with sweat, sebum forms the hydrolipidic film, a semi-aqueous, semi-greasy protective veil on the surface of the epidermis. However, although sebum is essential for the skin, excessive secretion leads to shiny areas, especially on the forehead, nose, and chin—namely, the T-zone. This surplus can cause dilation and blockage of skin pores, ultimately resulting in imperfections, such as open or closed comedones, even causing inflammatory lesions such as papules or pustules.

The oily skin is partly explained by genetic and hormonal factors, but can also be exacerbated by certain environmental factors, such as stress, an imbalanced diet, or the use of unsuitable cosmetic products that can stimulate sebum synthesis. That said, in most cases, oily skin results from excessive androgen production—male hormones that stimulate sebum synthesis—or from a hypersensitivity of the sebaceous glands to their action. Moreover, although oily skin is often perceived as thick and resilient, it can also suffer from a water imbalance: the abundant lipid film does not replace the water essential for maintaining the stratum corneum’s balance. It is therefore entirely possible to have dehydrated skin and oily at the same time.

A oily skin requires a gentle, balanced routine aimed at combating excessive sebum production without compromising its skin barrier.

Quite ambivalent, combination skin combines areas prone to oiliness with others that are drier or more normal. Most often, the T-zone is characterized by sebum overproduction leading to shine, enlarged pores, and sometimes localized blemishes. In contrast, the cheeks and temples display a completely different profile, with lower lipid production, a finer texture, and occasional signs of dryness. This duality of combination skin reflects an imbalance in sebaceous gland activity across facial regions, influenced by hormonal, genetic, and environmental factors.

Biologically, this uneven distribution of sebum can be explained by the variable density of sebaceous glands depending on the areas : they are more numerous and active in the T-zone, while less prominent on the cheeks. This disparity can be exacerbated by climate, lifestyle, or the use of inappropriate skincare products. Combination skin is undoubtedly the most challenging skin type to care for, as it reacts differently across its areas.

A combination skin requires treatments able to counteract excess sebum in the T-zone while preserving, or even restoring, hydration in the drier areas of the face.