How is the skin tone formed?
If you want to know how to whiten, you must first figure out how the skin’s complexion is formed. There are three main factors that determine skin color:
- The content of pigments such as melanin and carotene in the skin;
- Skin thickness and light scattering phenomenon on the skin surface;
- The content of blood oxygen and hemoglobin and reduced hemoglobin in the blood vessels of the dermis of the skin.
Among them, the main role is the melanin that we know well. Secondly, the thickness and roughness of the skin’s stratum corneum will also affect the apparent “color”. Therefore, the whitening approach mainly starts with melanin and stratum corneum.
Skin structure
Melanin is produced by melanocytes located in the basal layer of the epidermis. Melanocytes account for about 10% of basal cells. Each melanocyte extends to adjacent basal cells and spinous cells with dendritic protrusions to transport melanin particles.
The basic physiological process of melanin formation can be summarized as melanocytes produce melanin, melanin particles transfer to keratinocytes through melanocyte dendrites, and the melanin particles transferred to keratinocytes move up to the stratum corneum along with epidermal cells, thereby affecting the color and formation of the skin The stains are eventually excreted as the stratum corneum falls off. It is worth noting that the black produced in the basal layer does not cause visual “blackening”. Only when melanin is transferred to the stratum corneum can it cause visible “blackening” to the naked eye.
So how is melanin produced? Everything starts with one ingredient: Tyrosine. Tyrosine is catalyzed by tyrosinase and various oxidases to produce melanin in melanocytes. Part of the melanin produced moves up to the stratum corneum and then metabolizes it off, while the other part of the melanin moves down and is absorbed by the capillaries in the skin. , Excreted from the kidneys with blood circulation.
The specific production process of melanin is shown in the figure below. If you want to whiten, you only need to block the production or transfer of melanin to achieve the effect. Therefore, most of the various whitening ingredients inhibit, block or affect the link of melanin production to transfer. To achieve the corresponding effect, there are other products that quickly metabolize melanin from the skin to achieve a whitening effect.
Whitening mechanism of cosmetic ingredients
Melanin production mechanism
Control or inhibit the enzymes needed in each link in the process of melanin production
The enzyme is a kind of biocatalyst with extremely high catalytic efficiency. By inhibiting the activity of the enzyme, the entire biochemical reaction can be stopped or the reaction rate can be drastically reduced, thus inhibiting the necessary steps in the production of melanin in the cell. Enzymes are enough to hinder the production of melanin and effectively reduce the amount of melanin.
At present, most of the whitening ingredients target tyrosinase in the first two steps of the melanin synthesis reaction to inhibit its activity to achieve the whitening effect. The main ingredients with this kind of whitening mechanism are as follows: Arbutin and its derivatives Compounds, kojic acid and its derivatives, phenethyl resorcinol (377), licorice extract, hydroquinone (it has melanocyte toxicity, is more irritating and may cause skin leukoplakia, it has been banned from being added to cosmetics) and many more. In addition, some ingredients based on other whitening mechanisms may also have certain tyrosinase inhibitory activity.
Reduce the synthesized melanin or inhibit the self-oxidation of Dopa
The reducing agent can reduce the oxidation products in the melanin production process, and block the production of melanin by continuously reducing the oxidation products. At the same time, the reducing agent can also dilute the melanin and inhibit the production of dopaquinone, the oxidation product of dopa. In addition, the reducing agent can also inhibit the activity of free radicals caused by ultraviolet rays, haze, etc., thereby slowing down the oxidation of skin collagen, etc. Aging and dull complexion.
The ingredients with this kind of whitening mechanism mainly include vitamin C and its derivatives (can reduce oxidative melanin to colorless reducing melanin, and inhibit tyrosinase activity to a certain extent), oligomeric proanthocyanidins (more Baquinone reducing agent can reduce melanin and inhibit the formation of lipofuscin and senile plaques, and at the same time inhibit tyrosinase activity).
Inhibit the transport of melanin
If the melanin that has been produced cannot be transported to the stratum corneum (that is, the surface of the skin) smoothly, it will not cause visual “blackening”. Therefore, if the transport of melanin can be inhibited so that it cannot reach the surface of the skin, it will not cause blackening, which is another angle of whitening, melanin is produced, but it will not be seen by the naked eye.
Nicotinamide is the most famous ingredient with this kind of whitening mechanism. Niacinamide also has certain moisturizing, anti-acne, and anti-inflammatory effects, so it can improve the overall condition of the skin, but it has a certain irritation and can Stimulate facial hair growth, but also need to be used with caution.
Speed up skin metabolism and stratum corneum exfoliation
Even if the melanin that has been produced reaches the surface of the skin smoothly, there is another way to have a certain whitening effect, which is to speed up the skin metabolism and accelerate the shedding of the stratum corneum. The melanin that has reached the surface of the skin will fall off along with the stratum corneum cells. This method accelerates the metabolism of melanin, thereby improving skin color.
The whitening ingredients with this kind of mechanism are mostly acids, including the well-known: fruit acid, salicylic acid, etc. In addition, the whitening ingredients such as kojic acid and tranexamic acid also accelerate the metabolism of the stratum corneum due to their acidity. Effect. It should be noted that people with sensitive skin and thin stratum corneum should choose this method carefully to avoid excessive damage to the stratum corneum of the skin and cause more skin problems.
Selectively destroy melanocytes or change the structure of melanocytes
This type of method directly destroys melanocytes, causing their activity and function to be destroyed, and stopping the production of melanin.
Whitening ingredients with such mechanisms include Tranexamic acid (which also has a certain tyrosinase inhibitory activity), hydroquinone (which has been banned), etc.
Other indirect whitening
Including sunscreen, cut off the factors that induce melanin production to achieve the indirect whitening effect. Or increase the moisture content of the skin through moisturizing and other methods, maintain a moderate thickness of the stratum corneum, etc., so that more light reflected by the skin looks more shiny and translucent.
In short, the mechanism of whitening ingredients is all around the production and metabolism of melanin, and the whitening effect is achieved by controlling the various steps in the process of melanin production. A whitening ingredient may have multiple whitening mechanisms, but in the final analysis, they are inseparable from the categories summarized above.
The production of melanin itself is a self-defense mechanism of the skin. The skin forms a “protective umbrella” by producing melanin to prevent ultraviolet rays from causing deeper damage to the skin. Therefore, you must do a good job of sun protection while whitening.
In addition, the production of melanin is controlled by genetics and the environment. Do not over-pursue whitening effects and destroy the physiological functions of the skin itself, causing skin leukoplakia and other problems. When choosing a whitening product, you must see the whitening ingredients clearly, and choose a product that suits you reasonably.