Acne: What Green Tea Extract Brings to the Skin.

Acneis a skin condition that can affect the face, neck, back, or chest. It manifests itself through the appearance of spots, either red or white, and in severe cases, nodules or cysts. Generally speaking, acne results from an overproduction of sebum by the sebaceous glands. Although this substance is essential for maintaining skin hydration, an excess of sebum is also harmful as it can lead to the obstruction of skin pores. Unable to drain, the sebum remains in the hair follicle and sebaceous gland, promoting the appearance of blemishes.

Furthermore, this oily environment is conducive to the bacterial proliferation - particularly that of the bacterium Cutibacterium acnes. This microorganism, naturally present in the skin, digests the triglycerides in sebum and produces free fatty acids, which are responsible for inflammatory phenomena in the sebaceous glands. Finally, the process of desquamation or skin shedding is disrupted when one suffers from acne. This leads to an accumulation of dead cells on the skin surface, which can clog the pores.

The green tea extract (INCI: Camellia Sinensis Leaf Extract) is obtained from the leaves of the Camellia sinensis plant. The use of green tea dates back thousands of years in China, where it originates from. According to a legend, one day in the year 2737 BC, the Chinese Emperor Shen Nung was sitting under a tea tree and boiling water when suddenly, a leaf fell into his cup. Intrigued by the aroma, he decided to taste this beverage and was captivated by its flavour. In addition to its taste qualities, green tea extract has interesting properties for the skin and is often used in cosmetics, particularly for relieving acne.

A recent study has indeed shown that the application of a gel containing green tea extract, bamboo extract, and 5% lactic acid was beneficial in combating acne. For two weeks, 30 women aged between 19 and 23 years suffering from severe acne underwent five sonophoresis sessions per week, accompanied by the application of the gel. Sonophoresis is a technique that uses ultrasound to increase the permeability of the skin and to facilitate the diffusion of molecules. On average, scientists estimated that the severity of acne had decreased from 21.50 to 14.73, using the international GAGS system (Global Acne Grading System). Moreover, out of the 30 women, 25 transitioned from severe acne to moderate acne. The properties of the green tea extract, described below, thus contributed to alleviating this condition.

• The green tea extract has mattifying properties.

  Several researchers have demonstrated that green tea extract has a sebum-regulating effect, which is beneficial for individuals suffering from acne. Indeed, a reduction in sebum production is associated with a lower risk of pore obstruction, and therefore blemishes.

  A study notably followed ten individuals with oily skin. These individuals applied a cream containing 3% green tea extract to their cheeks daily for 8 weeks. This resulted in a 60% reduction in sebum production in this area. If we delve into the biological mechanisms at work, it appears that this result is due to the catechins present in the green tea extract. These polyphenols are indeed capable ofinhibiting the activity of 5-alpha-reductase. This enzyme catalyses the transformation of testosterone into dihydrotestosterone, which in turn activates the synthesis of sebum by the sebaceous glands.

• The green tea extract has anti-inflammatory activity.

  Catechins can also function by reducing the inflammation of the sebaceous glands caused by acne. These molecules indeed reduce the production of pro-inflammatory cytokines, such as interleukins 6 and 8 (IL-6 and IL-8) and the tumour necrosis factor (TNF-α), which are responsible for pathological phenomena. Furthermore, catechins decrease the activity of the nuclear factor kappa-B (NF-κB), a regulatory protein for several genes encoding for inflammation proteins.

• The green tea extract has an anti-bacterial effect.

  Green tea extract acts against certain bacteria, including Cutibacterium acnes, the bacterium involved in acne. Its antibacterial properties are largely due to its polyphenols, particularly catechins. These molecules appear to be capable of preventing pathogenic bacteria from binding to the host cell membrane. Furthermore, researchers have suggested that catechins may inhibit quorum sensing, that is, communication between bacteria.

• TJAMPAKASARI C. & al. Antimicrobial activity of green tea extract against isolates of methicillin-resistant Staphylococcus aureus and multi-drug resistant Pseudomonas aeruginosa. Asian Pacific journal of tropical biomedicine (2013).

• WILCZYNSKI S. & al. The Effects of Green Tea ( Camellia sinensis), Bamboo Extract ( Bambusa vulgaris) and Lactic Acid on Sebum Production in Young Women with Acne Vulgaris Using Sonophoresis Treatment. Healthcare (2022).

• FERNANDEZ-CAMPOS F. & al. Anti-Inflammatory and Anti-Quorum Sensing Effect of Camellia sinensis Callus Lysate for Treatment of Acne. Current issues in molecular biology (2023).