Very visible pores, skin that always looks oily and shiny, a complexion that’s often dull - does that sound familiar? Usually it all starts at adolescence, sometimes, but not always, beginning with blemish issues. Often it goes hand in hand with greasy hair - not surprising, as they’re caused by the same thing.
Sometimes the shininess only affects the T-zone - that's combination skin. Where does it come from, this skin imbalance that’s so hard to manage from day-to-day that it often turns into an obsession for both women and men?
For dermatologists, it’s physiological - in other words, oily skin naturally secretes too much sebum. Thus hyperseborrhoea, which causes oily skin, is endogenous first and foremost (that is, it results from internal causes), but it is also influenced by environmental factors. All the beauty problems connected with oily skin come from this quantitative imbalance of sebum, which is produced by the sebaceous glands in the dermis. Sebum plays a very important role in giving the skin natural protection and is one of the components of the epidermis's hydrolipidic film. Hydro for water, lipidic for fat: sebum is therefore the “fatty” part of the hydrolipidic film. What lies behind this excessive sebum production? 5 factors are inolved.
Influence of hormones
Sebum production is regulated by female hormones (oestrogens) slowing it down and male hormones (androgens) stimulating it. That’s why no-one ever has problems with oily skin before reaching puberty! Different mechanisms can lead to an increase in sebum secretion in both women and men. With women, for example, we often see runaway sebum production just before a period, when oestrogen levels fall and progesterone levels rise. On the other hand, during the period itself, women often experience drier skin.
Location on the body
The sebaceous glands are not distributed evenly across the body, which explains why some areas are very oily and others less so. As a rule, the areas with the most sebum are:
The same goes for the face, with an uneven distribution of the sebaceous glands resulting in varying sebum production. The highest level occurs in the T-zone (forehead, nose, chin) and cheeks, with there being less on the eyelids and neck. With oily skin, however, there is excess sebum all over the face. The T-zone only concerns cases of combination skin, where the skin is normal or dry on the rest of the face.
Gender
Sebum production starts earlier in girls, as they reach puberty earlier than boys do. On the other hand, men naturally produce more sebum than women once they are adults. Thus they very often suffer from oily skin.
Age
Hormonal activity really begins at puberty, which is the peak time for hormone secretion. Then things settle down during adulthood before gradually starting to reduce at the age of 45 for men, while women experience a sudden, drastic drop in production at the menopause.
Chronobiological rhythms & the environment
Sebum production varies during the day, peaking between 12 o’clock and 2 pm and dropping to its lowest between 4 am and 7 am. It also changes according to the seasons and the temperature, particularly with respect to heat. A 1°C increase in skin temperature increases sebum production by 10%. Not surprising, then, that the skin is shinier in spring and summer…
Food is also linked to sebum because the sebaceous glands use certain nutrients, such as glucose, acetates and fatty acids. A diet with a high glycemic index (rich in fast sugars) or that includes a lot of dairy produce (apart from cheese) indirectly increases lipid synthesis by the sebaceous glands.
Stress, difficulties and strong emotions can trigger an increase in body temperature and hence in seborrhoea. It's the same with alcohol.
In summer, sebum production often increases owing to the increase in skin temperature.
It seems parodoxical: your skin is all shiny yet your complexion is grey and lifeless. The explanation is a little technical, because it's to do with the reflection of light. Oily skin covered with a layer of sebum doesn’t reflect the light in the same way as other skin types.
To be precise, the skin sends all the rays of light back in the same direction - that of the angle at which the light arrived. It’s a real physics problem! Normal skin sends the light back in lots of different directions, and that's what makes it look radiant.
But with oily and combination skin, the focus is on the shiny areas, and, as the texture of the skin is irregular, less light is reflected, resulting in a dull, muddy complexion.
Pores are openings in the pilosebaceous follicle at the skin’s surface. There are said to be over a hundred thousand of them on the face alone (we don’t know who counted them!) Underneath lies a hair connected to a sebaceous gland.
If the sebaceous gland produces a lot of sebum, this natural exit enlarges to make it easier for the sebum to get out.
At the same time, pores naturally become distended as they age, partly because the skin begins to sag. They cannot be seen on a baby’s skin, but they double in size from the age of 25 to 50*.
*Journal of Dermatological Science – February 2016, Facial skin pores: a multiethnic study
