What are the benefits of azelaic acid for the skin?

Azelaic acid is often described as an ally for oily skin. It appears to have sebostatic properties, meaning an ability to limit the production of sebum by the sebaceous glands. This mechanism is particularly relevant for skin prone to blemishes, where an excess of sebum promotes pore blockage and the formation of comedones. By helping to regulate this lipid production, azelaic acid thus contributes to rebalancing the skin.

A clinical study conducted in 65 patients with mild to moderate acne specifically evaluated this sebostatic effect. Participants were divided into three groups, one of which applied azelaic acid once daily, with follow-up every two weeks. Sebum levels were measured using a sebumeter on different areas of the face. The results showed that azelaic acid made it possible to reduce sebum production to a moderate but significant extent.

Another study examined the effect of a 20% azelaic acid solution on sebaceous gland activity in 27 women with acne. The participants received six successive applications, with an assessment of sebum levels performed before and after the protocol. The results showed a progressive decrease in sebum levels. At the same time, a reduction in both the number and severity of acne lesions was observed. These findings support the hypothesis of a sustained sebostatic activity of azelaic acid, which may help limit the formation of new blemishes.

Note : The available data remain mixed regarding the effect of azelaic acid on sebum production. Some studies suggest that it does not directly reduce sebum secretion, but rather acts by modifying the composition of the surface lipid film, notably by decreasing the proportion of free fatty acids, which may contribute to a visually more matte appearance. Conversely, other work suggests a genuine sebum-regulating activity, in particular through inhibition of 5α-reductase, an enzyme involved in the local conversion of testosterone into 5-dihydrotestosterone, an androgen known to stimulate the activity of the sebaceous glands.

Keratinisation, also known as keratinocyte differentiation, is the process by which keratinocytes produced in the basal layer of the epidermis gradually migrate towards the surface while becoming progressively enriched in keratin. As they mature, these cells lose their nucleus and transform into corneocytes, which form the stratum corneum. This renewal is finely regulated in order to ensure even desquamation and an optimal barrier function. However, in certain situations, particularly in acne‑prone skin, this process may be altered. Cells then accumulate abnormally within the pilosebaceous canal, promoting pore blockage and the formation of comedones.

Azelaic acid may help by contributing to the normalisation of keratinisation.

This active ingredient acts in particular by modulating the proliferation and differentiation of keratinocytes, thereby limiting the hyperkeratinisation characteristic of skin prone to blemishes. This regulation helps to reduce the build-up of dead cells at the entrance to the follicles, which lowers the risk of forming open comedones, or blackheads, and closed comedones. This exfoliating action of azelaic acid also helps to even out skin texture and to combat a dull complexion, caused by poor reflection of light on the skin, particularly as a result of the accumulation of dead cells on its surface.

Azelaic acid has well-documented antibacterial properties, particularly against bacteria involved in blemishes, such as Cutibacterium acnes and Staphylococcus epidermidis. It acts by reducing their proliferation and by inhibiting their protein synthesis, a mechanism essential for their growth and survival. This activity is particularly relevant in the context of acne-prone skin, where the proliferation of these micro-organisms within the pilosebaceous follicle contributes to inflammation and lesion formation. By limiting this bacterial load, azelaic acid therefore helps to rebalance the skin microbiota and to slow the development of blemishes.

A study evaluated the effect of a cream containing 20% azelaic acid on the skin microbiota. After 8 weeks of application, a reduction of at least 96% in populations of C. acnes and S. epidermidis was observed both on the skin surface and at the follicular level.

In vitro data in vitro confirm these results, showing that azelaic acid slows the growth of these bacteria, while exerting a bacteriostatic and bactericidal activity. Its effectiveness depends on its concentration and on the pH of the environment, with enhanced activity in an acidic medium. Azelaic acid is moreover actively transported into the bacteria, where it targets protein synthesis, with significant inhibition observed at micromolar concentrations. Notably, no bacterial resistance has been demonstrated, even after a very large number of cell generations.

The antibacterial activity of azelaic acid provides an additional means of combating skin imperfections.

In addition, azelaic acid has anti-inflammatory properties which are based on different complementary mechanisms. It acts by inhibiting certain pro-inflammatory mediators, such as NF-κB, COX-2, TNF-α, IL-1β, IL-6 and IL-17, while promoting the expression of cytokines with an anti-inflammatory effect, such as IL-4 and IL-10. Furthermore, azelaic acid appears to be involved in the regulation of kallikrein-5 within keratinocytes, an enzyme implicated in the activation of cathelicidins, antimicrobial peptides whose dysregulation is associated with certain inflammatory skin conditions.

Azelaic acid soothes inflammatory responses and helps reduce redness, such as post-inflammatory erythema, as well as the symptoms of rosacea.

A clinical trial conducted in 160 subjects with rosacea compared the efficacy of a 15% azelaic acid gel with that of a 1% gel of metronidazole. Following daily application (once daily for metronidazole and twice daily for azelaic acid), both treatments showed a comparable reduction in the number of inflammatory lesions, with an 80% decrease for azelaic acid versus 77% for metronidazole. The reduction in erythema was also similar between the two groups (42.3% for azelaic acid versus 42.7% for metronidazole).

Azelaic acid is recognised for its depigmenting properties, which are particularly relevant in the case of dark spots, whether they are solar lentigines, melasma or post-inflammatory hyperpigmentation. This active ingredient inhibits tyrosinase, an enzyme involved in the synthesis of melanin. By limiting the activity of this enzyme, and also by modulating the expression of genes associated with melanogenesis, such as TYR, azelaic acid reduces melanin production within melanocytes. This leads to the gradual fading of pigment spots.

A double-blind, placebo-controlled clinical study conducted in 72 patients with mild to moderate acne evaluated the efficacy of a 15% azelaic acid gel applied twice daily for 12 weeks. The results show a significant decrease in the post-acne hyperpigmentation index (PAHPI) from week 8 onwards, with a more marked improvement than in the placebo group. A significant reduction in melanin content was also observed at 12 weeks. At the same time, a decrease in haemoglobin levels was measured in lesions of post-inflammatory erythema, indicating a reduction in redness. The study also demonstrates an improvement in patients’ quality of life and good tolerability, with no impairment of the skin barrier.

This study highlights the effects of azelaic acid on pigmentary disorders associated with inflammation.

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