Green tea, a friend to oily skin?

A skin is described as oily when it is constantly shiny and glossy. This is a result of an overproduction of sebum by the sebaceous glands. The sebaceous glands are accessory glands of the epidermis responsible for the secretion of sebum. They are present all over the skin surface at the dermis level, except on the palms of the hands and soles of the feet, known as glabrous areas. The overproduction of sebum is usually caused by endogenous factors, such as heredity or hormonal fluctuations.

Sebum is composed of lipids, primarily triglycerides, waxes which are esters of fatty acids and alcohols, and, to a lesser extent, squalene and cholesterol. Sebum is part of the hydrolipidic film present on the skin's surface, serving to protect it from external aggressions. Furthermore, it helps to maintain the skin's hydration and prevent insensible water loss. Therefore, sebum is essential for the skin.

However, when sebum is secreted in excess, it can lead to skin discomfort, such as theappearance of blemishes. Indeed, an excess of sebum can clog the skin's pores and promote bacterial proliferation - particularly that of Cutibacterium acnes, which plays a role in acne. Furthermore, oily skin is often a source of aesthetic concern due to the greasy appearance it imparts to the skin. Lastly, makeup often has more difficulty adhering to oily skin.

The green tea (INCI: Camellia Sinensis Leaf Extract), extracted from the leaves of Camellia sinensis, is a natural ingredient abundantly present in the cosmetics market. Antioxidant, mattifying, anti-inflammatory... Its properties are numerous. Green tea is indeed considered an ally for oily skin.

Several studies have explored the benefits of green tea and have concluded that this natural ingredient possesses sebum-regulating and mattifying properties. Indeed, in one of these studies, a group of 10 individuals with oily skin applied a cream containing 3% green tea extract to their cheeks daily for 8 weeks. The study revealed a significant reduction (≈ 60%) in sebum production in these individuals. From a mechanistic perspective, catechins, polyphenols found in green tea extract, inhibit the activity of 5-alpha-reductase. This enzyme catalyses the conversion of testosterone into dihydrotestosterone, which activates the synthesis of sebum by the sebaceous glands.

Another study, conducted over a shorter period, also highlighted the mattifying effect of green tea extract. In this one, 30 women applied a formulation based on green tea extract, bamboo extract, and 5% lactic acid five times a week for two weeks. Sonophoresis was used to enhance the absorption of the gel into the skin. Sonophoresis is a method that uses ultrasound to facilitate the diffusion of molecules into the epidermis. At the end of the two weeks, measurements taken with a sebumeter, a device capable of assessing the amount of sebum on the skin, showed that the gel had helped to reduce the amount of sebum in the areas where the gel had been applied. This went from an average of 170 µg/cm2 at the start of the study to 120 µg/cm2 after 2 weeks.

Therefore, the use of a skincare product containing green tea extract is beneficial for individuals with oily skin, as this ingredient aids inregulating sebum production and reducing the oily nature of the face and the dilation of pores, thus helping to prevent the onset of blemishes.

• SAEED T. & al. Outcomes of 3% green tea emulsion on skin sebum production in male volunteers.Journal of the association of basic medical sciences (2010).

• 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).