Acne is an inflammatory skin condition affecting the pilo-sebaceous follicles, which anchor each hair into the skin. Pilo-sebaceous follicles can be found across the entire surface of the body, except for the palms of the hands and the soles of the feet – on which pimples never form.

As its name suggests, a pilo-sebaceous follicle consists of a hair and a sebaceous gland, which secretes sebum. Acne is the result of an imbalance caused by several related phenomena: hyperseborrhoea (even though acne can also affect dry skin), dysseborrhoea, hyper-keratinisation, bacterial proliferation, as well as a genetic component.

Too much sebum pore

Hyperseborrhoea: this is the excess production of sebum resulting from hormonal activity triggered during puberty. The skin secretes very little sebum during childhood. The sebaceous glands become more active during puberty, when male sex hormones (androgens) start working, in girls as well as in boys. In most cases, excess sebum is then observed until hormonal balance is restored. The skin becomes oily and shiny, but this hyperseborrhoea alone cannot explain why acne occurs: some people have oily skin but no pimples!

Bad quality sebum pore

Dysseborrhoea: this is a change in sebum composition. Recently, researchers discovered a qualitative abnormality in the sebum of acne patients compared to healthy sebum. The sebum of people with acne lacks vitamin E, thus promoting skin-lipid oxidation. Since it becomes more difficult for sebum to flow outside of the follicle, it blocks the hair duct, and further increasing the risk of comedones.

Is acne only an oily-skin disease?

Yes and no. Blemishes are always caused by sebum problems. But with adult acne in particular, patients with fragile or dehydrated skin or even located scaly patches often experience both pimples and nodules. These lesions therefore cannot be simply attributed to the traditional biological causes.

In these cases, acne may be due to the effects of dysseborrhoea (which contributes to skin dehydration), an imbalance in the skin’s microbiome, poorly chosen cleansing or care products, or the side effects of undergoing years of harsh acne treatments.

  • Dr Michèle Sayag, allergologist
    Dr Michèle Sayag, Allergist.

    Yes, acne-prone skin can be sensitive!

    It’s true that blemished skin always has excess sebum and therefore tends to be oily. But recent discoveries involving dysseborrhoea have refined the approach. Current scientific knowledge confirms the feelings expressed by many acne patients, especially when the problem is long-lasting. They describe skin that has become intolerant, with some oily and other ultra-sensitive areas.

    Oily acne-prone skin is better understood today and is more complex than was once thought. It is a normal consequence of changes in the qualitative composition of sebum, causing transepidermal water loss to increase: oily skin can therefore be dehydrated.

    Lacking water, this oily skin is weakened and further stressed if it receives a drying acne treatment to combat blemishes.

    The skin is a living ecosystem... Keep in mind that the skin has a microbiome, i.e. skin flora made up of micro-organisms (bacteria, fungi, mites, etc.), that acts as a barrier against unwanted germs and protects against infection. But the slightest imbalance in this fragile environment can have major consequences and make way for “bad” bacteria. It is therefore not surprising that harsh local acne treatments modify the skin’s reactions. A subtler therapeutic strategy, taking into account the sensitivity of acne-prone skin, should therefore be adopted.

    Dr Michèle Sayag, Allergist.

Hyper-keratinisation, or thickening of the skin

Hyper-keratinisation refers to the excessive multiplication of skin cells in the follicle duct wall, causing a plug and thus keeping sebum from being evacuated properly.

The result is the formation of comedones, i.e. small bumps on the skin. These may be skin-coloured (closed comedones, whiteheads or microcysts), causing the skin to appear grainy, or else have a black centre (open comedones), due either to the oxidation of lipids exposed to air or to the presence of melanin (a skin pigment) on the comedo’s surface. Comedones may be black in colour due to the oxidation of lipids exposed to air. This stage corresponds to comedonal acne.


Bacterial proliferation, or the spread of microbes

Sebum is an ideal nutrient medium for certain bacteria, especially Cutibacterium acnes, more recently called Propionibacterium acnes.

Everyone has these bacteria on their skin. But the formation of a plug results in an ideal low-oxygen environment for these bacteria, which are then able to develop and proliferate in the pilo-sebaceous follicle.

The body defends itself through an inflammatory response. The comedo then turns into a painful red spot called a papule, sometimes topped with a pustule that contains a yellow fluid. This progression corresponds to inflammatory acne.

Mother and daughter sitting and together

It is commonly believed that acne has a genetic component and that there is familial predisposition. Sociological studies seem to confirm this idea, with an increased likelihood of inheriting acne from the mother for young girls under the age of 20 and for women aged 25 to 40 who have acne*.

Even though 46%* of adolescents between the ages of 12 and 19 confirm a family history of acne, there is currently no scientifically established genetic link.

*Arcane Research – February 2017