Everything you need to know about acne.

The leading reason for consulting a dermatologist, acne can cause a loss of self-confidence and significant psychological distress.

This common skin disease (for it is indeed a skin disease, and not merely a cosmetic concern) is characterised by excessive sebum production, disruption of normal cell turnover and the appearance of visible lesions, which may be inflammatory or non-inflammatory. Although it is often associated with adolescence, acne in fact affects a much broader population. Its prevalence in adult women has in particular increased in recent years, with estimates ranging from 12% to 54% depending on the study. In this context, acne may represent persistence of adolescent forms or may develop later in life, even in the absence of any prior history.

In adult women, acne presents with specific clinical features. It mainly affects the lower part of the face, with a predominance of inflammatory lesions, and often develops in relation to hormonal fluctuations of the menstrual cycle, with frequent worsening in the premenstrual period. Beyond the face, acne can also affect the trunk, particularly the back, chest, shoulders, upper arms and nape of the neck, through similar mechanisms, but exacerbated by mechanical factors such as sweating, occlusion or friction from clothing.

Truncal acne is common but often underestimated: more than half of individuals with facial acne also have it on the body.

It may be associated with more severe forms, which leave greater sequelae, such as atrophic or hypertrophic scars, as well as pigmentary disorders, such as post-inflammatory erythema or post-inflammatory hyperpigmentation, depending on the phototype. Beyond the cutaneous manifestations, the impact on quality of life is significant. The visibility of the lesions, particularly on exposed areas, can lead to social discomfort and influence certain daily activities, such as clothing choices or participation in social or sporting activities.

Acne is a chronic inflammatory dermatosis that originates in the pilosebaceous follicle.

One of the key mechanisms is follicular hyperkeratinisation: keratinocytes proliferate excessively and become more adherent, which hinders their elimination and leads to obstruction of the hair follicle. This phenomenon promotes the formation of a plug at the pore, which underlies comedone development. At the same time, individuals with acne often show increased sebum production, that is, hyperseborrhoea, and its composition is generally altered — a phenomenon referred to as dysseborrhoea, with an increase in squalene and free fatty acids and a decrease in linoleic acid. This more viscous sebum flows less easily, contributing to follicular blockage and local inflammation. Added to this is an imbalance in the skin microbiome, characterised by a loss of diversity among the subtypes of Cutibacterium acnes and a predominance of certain pro‑inflammatory strains, such as phylotype IA1.

Other internal factors contribute to the onset of acne. Hormones, particularly androgens, stimulate the activity of sebaceous glands and promote sebum production. Mediators such as IGF-1, whose levels rise especially during puberty, may also play a role by stimulating lipogenesis. In addition, substance P, released during periods of stress, is involved in the stimulation of sebocytes. Acne is also associated with an alteration of the skin barrier, with an increase in transepidermal water loss, indicating skin that is more permeable and often more reactive. Finally, genetics is an important susceptibility factor: a family history increases the risk of developing acne, sometimes in a more severe form.

In addition to these intrinsic factors, extrinsic factors may also contribute to worsening the lesions. Pollution, for example, generates oxidative stress, which promotes cutaneous inflammation. UV radiation may give the impression of a transient improvement by drying out certain lesions, but in reality it contributes to inflammation and to the impairment of the skin barrier. The role of diet remains debated, but some studies suggest a link between the consumption of fatty and sugary foods and a worsening of acne.

Acne is a progressive disease that develops in several successive stages within the pilosebaceous follicle. It generally begins with a phase of seborrhoea, corresponding to an excessive production of sebum. The skin then appears oilier, shiny, with enlarged pores, particularly on the T-zone of the face, that is to say, on the forehead, nose and chin. This excess sebum is rapidly accompanied by the formation of comedones, resulting from the accumulation of keratinocytes and lipids in the follicle. At this stage, certain bacteria such as Cutibacterium acnes find a favourable environment for their proliferation, setting the stage for the inflammatory phase to develop.

The earliest visible lesions of acne are comedones, which may be open or closed.

The open comedo, or blackhead, corresponds to a mixture of sebum and keratinised cells exposed to the air, whose dark colour results from the oxidation of lipids and the presence of melanin. The closed comedo, or whitehead, is characterised by a complete obstruction of the pore, preventing the evacuation of sebum and forming a small pale elevation. These non-inflammatory lesions often constitute the starting point of acne, which may then worsen, particularly when bacterial proliferation increases.

The inflammatory phase begins when the proliferation of C. acnes within the follicle leads to the release of pro‑inflammatory mediators. Various inflammatory lesions then appear. Papules are red, firm and sometimes painful spots, reflecting a superficial inflammation of the follicle. They may progress to pustules, which are characterised by the presence of visible pus at their apex. When the inflammation extends deeper, it can give rise to nodules, larger lesions that may form an abscess. In some cases, cysts may develop: these are encapsulated, often persistent lesions that are characteristic of severe forms of nodulo‑cystic acne.

Scars are the main complication of acne. The risk of developing them increases when the lesions are deep, inflammatory or picked at. They may initially appear red or pigmented, then progress to permanent forms. The most common scars are atrophic, forming depressions in the skin, but some individuals may develop hypertrophic or keloid scars.

Early management of acne reduces the risk of scarring.

The first step to take in the event of acne is to consult a dermatologist.

It is important to recall that acne is a chronic inflammatory disease, and not merely a cosmetic concern. While dermocosmetic or nutraceutical solutions can be helpful in the case of isolated blemishes, they remain insufficient for the management of true acne. In such cases, medical treatment is necessary to act on the various mechanisms involved and to limit the risk of scarring. Early management also helps to prevent the development of persistent or recurrent lesions.

The dermatologist adapts the treatment on a case‑by‑case basis, taking into account several criteria: the patient’s age, how long the disease has been present, the type of acne and its severity (often assessed using the GEA scale, from 0 to 5), its impact on quality of life, as well as any treatments that have already been used. Depending on these factors, three main therapeutic strategies may be proposed : topical treatment alone, a combination treatment associating topical care with an oral therapy, or a systemic treatment with isotretinoin. Once the acne is controlled, a maintenance treatment is generally recommended in order to reduce the risk of relapse.

Topical acne treatments, often prescribed as first-line therapy.

Topical treatments are generally the first-line approach, particularly for mild to moderate forms of acne. Among the most commonly used active agents are retinoids, such as tretinoin or adapalene, and benzoyl peroxide. Retinoids act by normalising keratinisation and reducing follicular blockage, while also exerting an anti-inflammatory effect. Benzoyl peroxide, for its part, has antibacterial activity against C. acnes, in addition to keratolytic and sebum-regulating effects. These treatments can be used alone or in combination. Azelaic acid is another interesting option, thanks to its keratolytic, anti-inflammatory and antimicrobial properties. Topical antibiotics may be prescribed for short courses, but their use should remain time-limited in order to reduce the risk of bacterial resistance.

The effectiveness of topical treatments cannot be evaluated before two to three months, and their introduction should be gradual in order to limit the risk of irritation.

Oral treatments for acne, intended for more severe or widespread forms.

In more extensive or inflammatory forms, an oral treatment may be combined with topical care. Oral antibiotics, particularly tetracyclines, are used for their anti-inflammatory properties, but their duration of prescription is limited because of the risk of resistance. Zinc may also be offered, with a more moderate level of efficacy. More recently, spironolactone, an anti-androgen used off-label in France, that is to say without specific official authorisation for the treatment of acne, although it is prescribed for this purpose, has shown promising results in adult women with moderate acne by reducing sebum production.

In cases of severe or treatment-resistant acne, a course of isotretinoin, a retinoid, may be considered. This is a powerful oral treatment that acts on all the mechanisms involved in acne, in particular by markedly reducing sebum production. It is prescribed for several months in order to reach a cumulative dose that helps limit relapses. However, its use requires close medical monitoring, with regular blood tests and strict precautions, especially because of its teratogenic effect. Effective contraception is therefore essential for women of childbearing age.

That said, isotretinoin is currently the only molecule that offers the potential for long-term remission of acne.

Are there other methods for treating acne?

Laser treatment can also be useful in cases of acne, but always within a medical setting. This technique should not be used as a first-line treatment or for self-medication; rather, it must be discussed with a dermatologist to ensure that it is appropriate for one’s individual situation. Several types of lasers have been shown to be effective on acne lesions.

• The Nd:YAG lasers (1,064 nm), pulsed dye lasers and KTP lasers act by targeting the vascularisation and the inflammation associated with the lesions.

• Other more recent devices (1,726 nm lasers) target the sebaceous glands more specifically in order to durably reduce sebum production. Encouraging results have been observed, including in moderate to severe acne, with improvements that may persist for several years after the treatment sessions.

• Photodynamic therapy (PDT) is another option. It is based on the application of a photosensitising agent, followed by exposure to a light source. This allows targeting of both the sebaceous glands and Cutibacterium acnes.

Despite promising results obtained in various clinical studies, it is important to remain cautious.

Scientific data remain heterogeneous, with variable protocols, sometimes limited sample sizes, and a lack of long-term follow‑up. These techniques furthermore require strict supervision, both to optimise their effectiveness and to limit their risks, particularly those related to pigmentation.

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