Which active ingredients should be used for oily skin (+)?

The oily skin (+) is a common dermatological concern. Although the sebaceous glands play an essential role in the skin’s barrier function by providing the stratum corneum with waterproofing properties, they are also responsible for excessive sebum production, resulting in an undesirable shiny appearance and enlarged pores. Many factors have been proposed to contribute to the pathogenesis of oily skin, and active ingredients have been identified to regulate this hyperseborrhea through various mechanisms of action.

Azelaic acid for long-lasting sebum regulation.

Theazelaic acid would be one of the substances that regulate sebaceous gland function. As demonstrated by a study conducted by ERKIERT-POLGUJ A. and colleagues in 27 women aged 19 to 25, topical application of six treatments with a 20% azelaic acid solution resulted in a significant reduction in sebum secretion levels. On the forehead, the mean sebum level was 195.5 before treatment and 162.7 after the six treatments; for cheek measurements, it averaged 175.3 before treatment versus 141.3 after the sixth application of azelaic acid.

The mechanism of action underlying this sebostatic effect is the inhibition of 5α-reductase, an enzyme that leads to increased androgenic activity accompanied by excessive sebum production (hyperseborrhea). It has been proposed that this inhibition occurs because azelaic acid can competitively occupy the NADPH binding site of 5α-reductase. Azelaic acid thus appears to represent a potential therapeutic agent for oily skin.

Bakuchiol, theplant-based analogue of retinol against excess sebum production.

Beyond its anti-aging and antioxidant properties, research in vitro has shown that the bakuchiol is capable of inhibiting three key pathways involved in acne pathogenesis, including the reduction of sebaceous gland activity. According to an in vivo study, its sebum-regulating mechanism of action is attributed to the negative regulation of 5-α-reductase expression, the enzyme strongly involved in sebum overproduction. At a concentration of 10 µg/mL, bakuchiol showed approximately a 40% reduction in the expression of this enzyme, an effect comparable to that of retinoic acid.

In a series of five clinical trials, one assessed the efficacy of a night serum containing 0.5% bakuchiol combined with melatonin and ascorbyl tetraisopalmitate in 31 participants with oily skin. After 28 days of application, sebum secretion decreased by 18.2%, demonstrating that the product is well suited for oily skin.

However, it is difficult to attribute the sebum reduction to bakuchiol alone, given the presence of other potentially synergistic actives and certain methodological limitations such as the absence of a placebo group. Moreover, clinical data remain limited and heterogeneous. Thus, although promising, bakuchiol still requires further research to confirm its sebum-regulating efficacy as a standalone ingredient.

L-carnitine to reduce sebum buildup.

Naturally produced in the body, L-carnitine plays a crucial role in human energy metabolism by enhancing β-oxidation, a catabolic process by which fatty acids are broken down. In an in vitro, human sebocytes were treated with 0.5% or 1% L-carnitine, resulting in a significant increase in β-oxidation and a concentration-dependent decrease in intracellular fatty acid content compared to untreated control cells, which would lead to reduced triglyceride accumulation in sebum lipid droplets.

To determine whether the data in vitro obtained could be applied to an in vivo, a randomized, vehicle‐controlled clinical trial was conducted on 21 participants. Volunteers applied a 2% L-carnitine formulation to half of their faces twice daily for three weeks. It was found that L-carnitine reduced sebum secretion rates compared with controls. Although further studies assessing the efficacy of L-carnitine’s sebum-suppressive properties are warranted, this ingredient appears promising for individuals concerned with oily skin.

Niacinamide (vitamin B3), the multifunctional active ingredient for regulating sebaceous lipogenesis.

To better understand the efficacy of niacinamide on acne, viable human tissues obtained from facelift surgeries were treated with niacinamide for four days. It was observed that niacinamide significantly reduces total sebaceous lipogenesis in a dose-dependent manner, an effect likely attributable to a reduction in triglycerides, which make up the predominant proportion of sebaceous gland lipids (up to 57.5%).

In addition, in 2006, a double-blind, placebo-controlled clinical study was conducted by SMILES K. and his team. It was demonstrated that the hydrophilic gel containing 2% nicotinamide and 1% D-panthenol, applied to the entire face twice daily in 100 subjects, significantly reduced sebum levels by about 30% after four weeks of use. Based on these initial data, the topical niacinamide appears to be useful for oily skin. However, further studies are necessary to describe the mechanism of action.

Retinoids to modulate sebocyte lipid synthesis.

The biological effects of retinoids on the skin rely on their ability to interact with nuclear receptors, namely the retinoic acid receptors (RAR; isoforms α, β, γ) which form heterodimers with retinoid X receptors (RXR; isoforms α, β, γ). In addition, one study found that all of these receptors are present in human sebocytes. Furthermore, a study in vitro demonstrated that retinoids can regulate sebocyte proliferation and differentiation by modulating keratin expression and lipid synthesis.

In view of this observation, it is therefore assumed that a topical retinoid would bind to these specific receptors on sebocytes, thereby causing a reduction in sebum production. However, there is currently no direct evidence demonstrating that topical retinoids clearly have a sebo-suppressive effect.

Sarcosine, an amino derivative that controls surface hyperseborrhea.

The sarcosine is the N-methyl derivative of glycine, an amino acid naturally present in human body tissues. It has been reported as a promising ingredient for rebalancing oily skin. According to certain studies, when applied topically, sarcosine regulates excess sebum, shine, and greasiness of the skin. It exerts this effect by inhibiting the activity of 5α-reductase, an enzyme responsible for converting testosterone into dihydrotestosterone, which in turn promotes sebum production.

In fact, a clinical study conducted on women aged 21 to 49 years demonstrated a statistically significant reduction in sebum levels on the skin surface after two weeks of twice-daily application of a topical formulation containing sarcosine. Nevertheless, while this preliminary study is promising, further investigations are necessary to better understand the sebostatic action of sarcosine on oily skin.

Green tea and its sebum-regulating potential.

Another ingredient whose application to oily skin has been proven is green tea (Camellia sinensis). In a small 2010 study, 10 male volunteers applied a topical emulsion containing 3% ethanol extract of green tea to their cheeks over an eight‐week period. A statistically significant reduction in skin sebum production (≈60%) compared to baseline was observed throughout the study.

Another study with a slightly larger cohort (n = 22 male participants) also revealed a consistent and significant reduction in sebum secretion after 60 days of applying a topical green tea emulsion to one side of the face. Based on these findings, topically applied green tea proves beneficial for individuals with oily skin. It is suggested that this activity is due to the ability of epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), the main active constituents of green tea, to selectively inhibit the enzyme 5 α-reductase in the sebaceous glands.

Vitamin D and its analogs: a new strategy against excess sebum?

Human sebocytes, the cells responsible for production of sebum, are thought to express vitamin D receptors (VDR) as well as the enzymes required for synthesis and metabolism of its biologically active form (calcitriol). Studies in vitro have shown that exposure to calcitriol or certain vitamin D analogues can slow sebocyte proliferation, arrest their growth cycle, and reduce lipid production in a dose-dependent manner, suggesting a potential seboregulating effect.

However, it is important to emphasize that these findings derive exclusively from studies conducted on cellular models in vitro. To date, no clinical study has confirmed these effects in humans. Further research will therefore be necessary to confirm their potential as topical actives intended for oily skin.

Zinc, atrace element with anti-androgenic and sebo-suppressive action.

Some studies seem to indicate that thetrace element zinc may have sebo-suppressive activity. Indeed, findings have shown that it plays a regulatory role in testosterone metabolism with a local antiandrogenic effect. It has been reported in particular that zinc can inhibit, in vitro, the enzymatic activity of 5α-reductase, which is mainly present in sebaceous glands, in a dose-dependent manner through different mechanisms.

Although additional data are needed to confirm zinc’s effect on sebum production, an initial randomized, double-blind clinical trial reported that topical application of a lotion containing a 4% erythromycin and 1.2% zinc complex in 14 volunteers led to a significant reduction in sebum excretion rate—by over 20% compared to the control lotion (4% erythromycin)—after 12 weeks. These findings suggest that the effect on sebum production may be attributed to the zinc in the formulation.

Besides these actives, there are also ingredients known as mattifying (sulfur, silica, clay, charcoal, bamboo extract, etc.), capable of reducing the shiny appearance of oily skin more by absorbing excess sebum from the skin’s surface.

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