Beauty

Lactic acid is softer than glycolic acid. It is formed during the fermentation of substances such as whey, dextrose, starch, molasses. In industry, it is obtained from acrylonitrile, a substance widely used in the production of various kinds of plastic fibers. Lactic acid, along with citric, oxalic and grape acid, was among the first discovered and studied organic acids. This work was carried out in 1780 by the Swedish chemist Carl Scheele (1742-1786). Lactic acid is found in large quantities in milk, hence its name. In addition, lactic acid is present in bread, cheese, meat, beer and wine.

In the human body, lactic acid is found in fairly large quantities, since it is one of the intermediate products of carbohydrate metabolism. (Some lactic acid is found in the air we exhale, which helps mosquitoes detect us.) The skin contains quite a lot of lactic acid, which, in fact, is the main water-soluble acid of the epidermis and is important for its normal functioning.

Therefore, treatment of the skin with lactic acid can compensate for the possible lack of this substance. Lactic acid helps treat sunburn, and also reduces wrinkles and liver spots (the common name for the brown spots that form with age where melanin accumulates). Lactic acid is sometimes added to shaving creams and used to lighten freckles.

The mechanism of action of lactic acid is that it penetrates the skin and weakens the hydrogen bonds that hold cells together, as a result, the surface layers of the skin become looser, after which they can be easily washed off. In addition, lactic acid increases the degree of hydration of the surface layers of the skin by increasing the extensibility of tissues and their ability to retain water. As a result, the skin dries less, does not peel off and does not crack. Lactic acid also opens the skin pores, softens the skin and improves its tone.

The lactic acid solution is specially buffered in order to stabilize the pH at such a level that the cosmetic does not irritate the skin, but is still acidic enough to work. Most formulations based on AHA have a pH of about 3-4, these values ​​are considered optimal. The buffering properties of cosmetic products based on lactic acid are usually set by adding sodium lactate.

Salts of lactic acid are used in the production of hygiene products: potassium lactate, for example, allows you to thicken shampoos and washing gels. Silver lactate is part of anti-dandruff products, and zirconium lactate is a good antiperspirant.

There are other derivatives of lactic acid that have found application in cosmetics. Esters such as butyl lactate, lauryl lactate and myristyl lactate help to make the skin soft and smooth. And ethyl lactate ester is widely used as a solvent.

So, do AGKs really work? The answer to this question is yes. The results of a double-blind study conducted by Matt Stiller were reported in the 1996 Archives of Dermatology. The scientist studied the effect of 8% solutions of AHA on seventy-three women aged 40 to 70 years, all of whom had excessive exposure to sunlight during their lives. Stiller concluded that AHA treatment of the skin daily for six months led to a clear improvement in its condition, but the rejuvenating effect of the acids was rather limited. Lynn Drake of the University of Oklahoma gave a talk on AHA at the 55th annual convention of the American Academy of Dermatology in 1997.

In the report, she reported that her double-blind study of creams containing 8% glycolic or lactic acid showed that the tested cosmetics improved the skin condition to a small extent, but significantly, especially in people who had previously been exposed to excessive sun exposure.

And in conclusion, we should mention the beta-hydroxy acids BHA, which, like their alpha counterparts, contribute to the desquamation of the epithelium. Some scientists believe that beta-hydroxy acids are better for wrinkling without any irritating effect, so these substances are sometimes used along with AHA. But so far there is no convincing evidence of the advantage of BHA over AHA.

Source: based on the book by John Emsley «On the benefits and harms of the products we love to buy»

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