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 it can limit the production of sebum by the sebaceous glands. This mechanism is particularly relevant for skin prone to blemishes, where excess sebum promotes pore clogging and the formation of comedones. By helping regulate this lipid production, azelaic acid contributes to rebalancing the skin.

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

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 quantity before and after the treatment 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 lasting 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 decrease sebum secretion, but instead acts by modifying the composition of the surface lipid film, notably by reducing the proportion of free fatty acids, which may contribute to a visually more matte appearance. Conversely, other studies propose 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 sebaceous gland activity.

Keratinization, also called keratinocyte differentiation, is the process by which keratinocytes produced in the basal layer of the epidermis gradually migrate toward the surface while becoming loaded with keratin. Over the course of this maturation, these cells lose their nucleus and become corneocytes, forming the stratum corneum. This renewal is finely regulated to ensure uniform desquamation and an optimal barrier function. However, in certain cases, particularly in acne-prone skin, this process can be altered. Cells then accumulate abnormally within the pilosebaceous canal, promoting pore blockage and the formation of comedones.

The azelaic acid may help by contributing to the normalization of keratinization.

This active ingredient acts in particular by modulating the proliferation and differentiation of keratinocytes, thereby limiting the hyperkeratinization characteristic of blemish-prone skin. This regulation helps to reduce the buildup of dead cells at the opening of 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 helps combat a dull complexion, caused by poor light reflection on the skin, especially as a result of dead cell buildup on its surface.

Azelaic acid has well-documented antibacterial properties, particularly against bacteria involved in skin blemishes, such as Cutibacterium acnes and Staphylococcus epidermidis. It works by reducing their proliferation and inhibiting their protein synthesis, a mechanism that is essential for their growth and survival. This activity is especially relevant for acne-prone skin, where the overgrowth of these microorganisms within the pilosebaceous follicle contributes to inflammation and lesion formation. By limiting this bacterial load, azelaic acid helps rebalance the skin microbiome and 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 the populations of C. acnes and S. epidermidis was observed on the skin surface and at the follicular level.

In vitro data support these findings, 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 under acidic conditions. Azelaic acid is also actively transported into bacterial cells, where it targets protein synthesis, with significant inhibition observed at micromolar concentrations. Notably, no bacterial resistance has been detected, even after a very large number of cell generations.

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

Furthermore, azelaic acid has anti-inflammatory properties that rely on several 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 anti-inflammatory effects, such as IL-4 and IL-10. In addition, azelaic acid appears to be involved in the regulation of kallikrein-5 in keratinocytes, an enzyme involved in the activation of cathelicidins, antimicrobial peptides whose dysregulation is associated with certain skin inflammations.

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

A clinical trial conducted in 160 subjects with rosacea compared the effectiveness of a 15% azelaic acid gel with that of a 1% gel of metronidazole. After daily application (once per day for metronidazole and twice per day for azelaic acid), both treatments showed a comparable reduction in the number of inflammatory lesions, with a decrease of 80% 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 known for its depigmenting properties, which are particularly useful 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 melanin synthesis. 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 gradually helps fade pigmentation spots.

A double-blind, placebo-controlled clinical trial 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) as early as week 8, with a more pronounced 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 hemoglobin levels was measured in lesions of post-inflammatory erythema, indicating a reduction in redness. The study also highlights 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 related to inflammation.

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