Skin lightening creams
Along with substances that create an artificial tan, there are those that allow you to make the skin lighter.
One of the signs of aging are small melanin spots on the skin, which are also called liver spots. To stop their formation, it is necessary to block the metabolic process of melanin formation. This means that you need to inhibit the enzyme tyrosinase (another name is phenol oxidase), which catalyzes the conversion of tyrosine to melanin. Tyrosinase is widely distributed in nature, it is produced in plants, animals and humans. It is thanks to this enzyme that the apple turns brown on the cut. If the active center of tyrosinase, which contains a copper atom, is neutralized, the enzyme will lose its oxidizing properties. Therefore, if you cut an apple and drip it on a slice of lemon juice, the slice will remain white because the vitamin C in lemon juice deactivates tyrosinase. This is why lemon juice is traditionally used for skin lightening.
Other reasons to resort to skin lightening lotions are excessive freckling, pregnancy spots and even excessive sunburn, as well as some diseases that cause the skin to become dark in color.
A standard lightening cream contains one of the well-known tyrosinase inhibitors, such as kojic acid or hydroquinone, plus glycolic acid, which helps to remove the top layers of the skin and allows the inhibitor to reach target cells. The composition of the product usually also includes a preservative and a number of other ingredients: a solvent, vitamins and flavorings.
In the past, the effect of lightening dark skin was easily achieved by applying hydroquinone, a chemical widely used in photography, to the skin. Today, it is not recommended to use this method, since the harmful effects of hydroquinone on the human body have been noticed. The old name of hydroquinone is quinol, it was previously produced under the trademarks Aida, Black and White, Eldopaque, Tecquinol.
Hydroquinone is a white crystalline substance, soluble in water and alcohol, its melting point is 171°C. At low concentrations, hydroquinone solution whitens the skin, but some people develop dermatitis, so products containing hydroquinone are banned in Europe, the United States, and Japan. In other countries, cosmetic preparations with hydroquinone are allowed, but the concentration of the active substance in them should not exceed 2%, however, at such a low concentration, brightening agents are ineffective. Similar in properties to hydroquinone, but safer substances such as THPOF (abbreviation for 4-(tetrahydropyran-2-yl)oxyphenol) are patented as skin lightening agents, but products based on them have not yet appeared on the market.
Several natural skin lighteners exist, including kojic acid, licorice extract, skullcap extract, mulberry extract, and tyrosinase inhibition. Kojic acid is produced by the bacterium Aspergillus oryzae and is used as a skin lightener and antibiotic, and is also used to make maltol, a flavoring in baked goods. All natural brightening agents are almost as effective as hydroquinone, for clarity, we compare their inhibitory effects on tyrosinase. A 5% solution of hydroquinone inhibits tyrazinase by 50%, a 10% solution of kojic acid and a 0.5% solution of mulberry extract inhibit the enzyme to the same extent.
To achieve a noticeable brightening effect, it is necessary to use any of the natural brighteners for several weeks, and it is important that the cosmetic product contains a substance that facilitates the penetration of the brightener into the skin. In addition, the composition of the agent should include a buffer agent to maintain pH at 4 and an antioxidant, such as pyrosulfite, which allows the agent to retain its properties for a long time.
In parts of Africa, people who have very dark skin use mercury iodide soap to lighten even a little. At the same time, they lather all night. Now such soap is prohibited, as it harms the health of both those who use it and those who produce it. In the 1970s, a medical examination of soap factory workers was carried out, which revealed high levels of mercury in their blood. And at the University of Lausanne in Switzerland, consumers of mercury iodide soap were examined, and mercury was also found in their blood and urine, indicating the ability of the heavy metal to penetrate the skin.
Source: based on materials from John Emsley’s book «On the benefits and harms of the products we love to buy»
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