Everything you need to know about acne.

Acne is the leading reason for consulting a dermatologist and can lead to a lack of self-confidence and significant psychological distress.

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

In adult women, acne shows specific clinical characteristics. It mainly affects the lower face, with a predominance of inflammatory lesions, and often develops in association with 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—with similar underlying mechanisms, but aggravated 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 acne on their body.

It can be associated with more severe forms, which leave more lasting aftereffects, 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, especially on exposed areas, can cause social discomfort and influence certain daily activities, such as clothing choices or participation in social or sports activities.

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

One of the key mechanisms is follicular hyperkeratinization: keratinocytes proliferate excessively and become more adhesive, which interferes with their elimination and leads to blockage of the hair follicle. This process promotes the formation of a plug at the pore, which gives rise to comedones. At the same time, individuals with acne often have increased sebum production, known as hyperséborrhea, and its composition is typically altered—a phenomenon referred to as dysseborrhea, characterized by elevated levels of squalene and free fatty acids and reduced levels of linoleic acid. This more viscous sebum flows less easily, contributing to follicular obstruction and local inflammation. In addition, there is an imbalance of the skin microbiome, marked 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 the 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 stimulating 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, there are extrinsic factors that can worsen the lesions. Pollution, for example, generates oxidative stress, which promotes skin inflammation. UV rays may give the impression of a temporary improvement by drying out certain lesions, but in reality they contribute to inflammation and to the impairment of the skin barrier. The role of diet remains under debate, 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 seborrhea, corresponding to an excessive production of sebum. The skin then appears oilier, shiny, with enlarged pores, particularly in the T-zone of the face, that is, on the forehead, nose, and chin. This excess sebum is quickly 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 favorable environment for their proliferation, setting the stage for the inflammatory phase.

The first visible lesions of acne are comedones, which can be open or closed.

The open comedo, or blackhead, corresponds to a mixture of sebum and keratinized cells exposed to the air, whose dark color results from the oxidation of lipids and the presence of melanin. The closed comedo, or whitehead, is characterized by a complete blockage of the pore, which prevents the evacuation of sebum and forms a small pale bump. These non-inflammatory lesions often represent the starting point of acne, which can then worsen, particularly when bacterial proliferation increases.

The inflammatory phase begins when the multiplication 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 bumps that indicate a superficial inflammation of the follicle. They can progress to pustules, which are characterized by visible pus at their surface. When the inflammation extends deeper into the skin, 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 typical of severe forms of nodulocystic 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 more permanent forms. The most common scars are atrophic, forming depressions in the skin, but some people may develop hypertrophic or keloid scars.

Early management of acne reduces the risk of scarring.

The first step when dealing with acne is to consult a dermatologist.

It is important to remember that acne is a chronic inflammatory disease, not just a simple cosmetic concern. While dermocosmetic or nutraceutical products can be helpful for isolated blemishes, they are not sufficient to manage true acne. In such cases, medical treatment is necessary to target the different mechanisms involved and to reduce the risk of scarring. Early management also helps prevent the development of persistent or recurrent lesions.

The dermatologist adjusts 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 treatments that have already been used. Based on these factors, three main therapeutic strategies can be proposed : topical treatment alone, a combination treatment that associates topical care with an oral medication, or systemic treatment with isotretinoin. Once the acne is under control, a maintenance treatment is generally recommended in order to limit relapses.

Topical acne treatments, often prescribed as the first-line option.

Topical treatments are generally the first-line approach, especially for mild to moderate forms of acne. Among the most commonly used active ingredients are retinoids, such as tretinoin or adapalene, and benzoyl peroxide. Retinoids work by normalizing keratinization 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 valuable option, thanks to its keratolytic, anti-inflammatory, and antimicrobial properties. Topical antibiotics may be prescribed occasionally, but their use should be limited in duration 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 to limit the risk of irritation.

Oral treatments for acne, 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 use is limited because of the risk of antibiotic resistance. Zinc can also be prescribed, with a more moderate level of effectiveness. More recently, spironolactone, an anti-androgen used off-label in France—that is, without a specific official authorization for the treatment of acne, even though 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, therapy with isotretinoin, a retinoid, may be considered. This is a powerful oral medication that acts on all of the mechanisms involved in acne, notably by greatly reducing sebum production. It is prescribed over several months in order to reach a cumulative dose that helps limit relapses. However, its use requires strict medical supervision, including regular laboratory tests and strict safety precautions, particularly because of its teratogenic effect. Effective contraception is therefore essential for women of childbearing potential.

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

Are there other methods to treat 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 the patient’s individual situation. Several types of lasers have demonstrated effectiveness in treating acne lesions.

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

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

• Photodynamic therapy (PDT) is another option. It is based on the application of a photosensitizing agent, followed by exposure to a light source. This makes it possible to target 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 also require strict supervision, both to optimize their effectiveness and to limit their risks, particularly those related to pigmentation.

• ZOUBOULIS C. C. Acne and sebaceous gland function. Clinics in Dermatology (2004).

• THIBOUTOT D. & al. Acne: Hormonal concepts and therapy. Clinics in Dermatology (2004).

• GARNER S. & al. Acne vulgaris. The Lancet (2012).

• RADEMAKER M. & al. Isotretinoin: dose, duration and relapse. What does 30 years of usage tell us? Australasian Journal of Dermatology (2012).

• POTENZA C. & al. Adult acne versus adolescent acne. Journal of Clinical and Aesthetic Dermatology (2018).

• BENSON H. & al. Targeted topical delivery of retinoids in the management of acne vulgaris: Current formulations and novel delivery systems. Pharmaceutics (2019).

• ZOUBOULIS C. & al. Endocrinology and immunology of acne: Two sides of the same coin. Experimental Dermatology (2020).

• SHAH A. & al. ScarNet: Development and validation of a novel deep CNN model for acne scar classification with a new dataset. IEEE Access (2021).

• HSU J. & al. The use of lasers and light devices in acne management: An update. American Journal of Clinical Dermatology (2021).

• DOVER J. & al. Novel 1726 nm laser demonstrates durable therapeutic outcomes and tolerability for moderate-to-severe acne across skin types. Journal of the American Academy of Dermatology (2023).

• NGUYEN P. & al. ACNE8M - An acnes detection and differential diagnosis system using AI technologies. Science and Technology Development Journal (2024).