To win the battle against blemishes once and for all, we must consider the various mechanisms of action involved in acne. We’re here to help you understand the causes of acne, learn more about who is affected, and recognise its various types!


What are the 4 causes of acne?

Did you look at the mirror this morning just to discover a nasty pimple that sprang up overnight? Do you want to know where it came from? It is due to an anomaly of the pilo-sebaceous follicles, in charge of secreting sebum, which protects our skin. Pilo-sebaceous follicles can be found on almost the entire body (especially the scalp, face, chest and upper back). Each one contains a hair that is connected by a hair duct to a sebaceous gland, which itself is located below the epidermis.

With healthy skin, a normal and sufficient amount of sebum is produced. It flows outward to form the protective hydrolipidic film. Things are just as they should be! But the activity of these sebaceous glands is controlled by the hormones, male one’s in particular. With this in mind, there can be four types of dysfunctions, which usually occur simultaneously.


Too much sebum pore

1. Too much or excess sebum

Sebum can be over-produced in subjects with oily skin as well as during adolescence and puberty. This is hyperseborrhoea: the skin produces too much sebum and becomes shiny. Its pores become dilated and there is a risk of this excess sebum easily clogging the hair duct that is usually responsible for its evacuation.

Bad quality sebum pore

2. Poor-quality sebum

Sebum quality also plays a role in the development of blemishes. Studies on this topic have shown that the sebum of acne patients is not the same compare to people with healthy skin. Sebum composition in acne patients lacks vitamin E, making the lipids in sebum, squalene in particular, more susceptible to oxidation. This sebum is highly comedogenic and irritating to the skin. The phenomenon by which sebum becomes altered is called dysseborrhoea.

Clogged pore

3. Clogged pores

In parallel, a hyper-keratinisation process thickens the skin: skin cells multiply and this overproduction ends up blocking the hair duct. As a result, sebum can no longer flow normally and comedones form under the skin. If they are open, they are blackheads. If they are closed, they are whiteheads or microcysts.

Inflamed pore

4. A progression to inflammatory acne

Lastly, there are bacteria that easily proliferate in the hair follicles of oily or acne-prone skin since sebum is a highly favourable medium for them. Acne specialists have identified a bacterium particularly correlated with the characteristic dysseborrhoea of acne-prone skin: Cutibacterium acnes, called Propionibacterium acnes until only recently. Sebum whose composition has been altered causes it to multiply in the sebaceous gland. The bacterial population is then imbalanced. As always in the event of infection, the body responds with inflammation. This is the final stage of inflammatory acne, which turns the basic comedo into an inflamed red spot, called a papule by dermatologists.

New discoveries regarding the origins of acne

Excess sebum, stress, diet, pollution: in light of the very sharp increase in cases of acne in adults over the age of 30, new hypotheses, beyond the biological processes described above, have recently emerged to explain this adult acne.

Dermatologists have thus highlighted other potential factors, such as environmental pollution, modern nutrition, or stress. In many cases, these are still assumptions that will need to be confirmed by further studies.


Pollution is directly involved in several skin diseases and may also play a role in sebum composition. Indeed, since the epidermis is permeable, it is not impervious to the external environment. Among other things, environmental pollution can impact the nature of sebum and therefore the skin microbiome, generating imbalances between the good and bad bacteria that live on the skin’s surface.


Diet has long been suspected of playing a role in acne. Once again, recent studies seem to confirm this suspicion. Dairy products and sugar in particular should be avoided by patients with inflammatory acne.


Chronic stress has a real impact on biological balances. Some say that testosterone production has increased in adult women in relation to lifestyle changes. This increase in male hormones would then explain the rise in cases of adult acne in women.

Adults, adolescents, infants: who is affected by acne?

Teenagers, of course! But they’re not alone. Acne seems to be becoming more and more widespread, affecting an increasing number of adults all around the world, especially in Asia. Some even say it is a global epidemic.


Adolescent acne

This is extremely widespread and caused primarily by hormonal activation during puberty, with androgen secretion in both girls and boys.
“Signs of acne generally begin to appear between the ages of 12 and 15, in 69% of cases*”.

However, over the past few years, doctors have noted that acne problems are tending to start at younger ages than in the past, due to an increase in the number of cases of early puberty.
In adolescence, excess sebum production is followed by first acne lesions, typically taking the form of comedonal acne with blackheads and microcysts in particular. Over time, these may progress to inflammatory lesions as a result of bacterial proliferation. Pimples and blemishes are located on the face, cleavage and back and sometimes the shoulders and chest.

Often uncontrolled throughout this period, hormonal production usually regulates itself within a few years, which is why problems involving acne blemishes in adolescents tend to spontaneously disappear at the end of puberty.

*Arcane Research study France– February 2017


Adult acne

“1 in 4 people between the ages of 20 and 40 years claims to have acne*”.

This is sometimes caused by a persistent hormonal imbalance, but such cases are relatively few in number and are accompanied by other distinctive symptoms such as excessive hair growth, hair loss, or significant weight gain in women.

There are some other specific cases including pregnant women, who experience hormonal disruptions capable of causing acne to recur, during or even after pregnancy. This massive shift in hormones is also responsible for infant acne, which can sometimes be seen after birth and then naturally disappears without requiring any treatment.

Acne can also be triggered in some adults who never experienced problems during adolescence. There are other cases of adults who never got rid of their adolescent acne.
In fact, there is such a wide variety of situations that experts wonder whether there really are any specific causes of adult acne. This adult acne does indeed have a strong inflammatory component, even though blackheads are also present and deep cysts are more common.

It is now known that the lesions of this type of acne are actually quite similar to those of acne in adolescents: they include blackheads, microcysts, papules, and pustules. Note, however, that they are more likely to be found on the lower face, along the jaws and on the chin in adult women and on the upper back in adult men.

The causes of this adult acne are still poorly understood, but there seems to be a set of unfavourable factors acting in synergy.

*Arcane Research study France – February 2017


How to identify the various types of acne

Acne blemishes are classified into several types, but deciphering them can be difficult as they often coexist at the same time. Comedonal acne, inflammatory acne, cystic acne, etc. Learn how to identify each type of pimple and call it by its name...

Woman with pimple

Comedonal acne

Its distinguishing features: shiny skin due to excess sebum, very visible and highly dilated pores, as well as comedones. The latter are classified into one of two types: open comedones (blackheads) or closed comedones (microcysts under the skin that are visible on the surface).
Blackheads owe their colour to the oxidation of lipids exposed to air. As for microcysts, they are either white or red depending on the level of infection.

Woman with light acne

Inflammatory acne

Its distinguishing feature: painful red spots on the skin. This type of pimple corresponds to the stage following comedonal acne, when the Cutibacterium acnes bacterium proliferates in the lesions and triggers an inflammatory reaction. Depending on their progression, these pimples are called papules, pustules or nodules.

Rare and severe forms of acne

  • Acne conglobata is a variant of nodular acne, which affects males either in adolescence or between the ages of 18 and 30. Still unexplained, it starts out as very pronounced hyperseborrhoea and is associated with all types of lesions, which rapidly become inflammatory. Deep inter-connected cysts sometimes cause abscesses. It is primarily located on the back but can quickly spread from the shoulders to the abdomen and buttocks. Acne conglobata can be treated but usually leads to significant scarring.
  • Acne fulminans is more likely to affect adolescent boys. It is an acute form of acne that presents as inflamed and infected nodules with fever and joint pain. It requires antibiotic treatment.