How to Use Lactic Acid for Skin?

Lactic acid in skin care is found in many formulations under the INCI name “Lactic Acid”. It is an organic acid from the alpha-hydroxy acid (AHA) family, like glycolic acid for example. It is found naturally in milk (from which it was first extracted), certain fruits and vegetables and wine. It is also present in the human body. It is involved in many biochemical processes and is part of the Natural Moisturizing Factor (NMF).

Note: The NMF or Natural Moisturizing Factor represents 30% of the total dry weight of the stratum corneum. It is composed of amino acids, their derivatives and extracellular compounds such as lactic acid or urea. Its hygroscopic properties allow it to capture and retain water in the stratum corneum, thus maintaining good skin hydration.

What is lactic acid used for?

Lactic acid can be used for various skin problems because of its multiple benefits and high tolerance:

• For skin with imperfections (blackheads, pimples, acne scars) and dull complexion:

Although acne is a multifactorial inflammatory disease, hyperseborrhea (excessive production of sebum) is one of the major factors. Indeed, sebum is a nutritive environment favorable to the growth of the bacteria responsible for acne, Cutibacterium acnes. Furthermore, an excess of sebum slows down the natural process of skin renewal (desquamation). The sebum will thus tend to block the pores of the skin which supports the appearance of imperfections.

Lactic acid, thanks to its keratolytic properties, stimulates cell renewal by eliminating dead cells on the surface of the epidermis. This gentle chemical exfoliation eliminates imperfections and revives the radiance of the complexion.

A scientific study has proven that 

the application of products containing 

2% lactic acid twice a day for 12 weeks

reduces blackheads by 56%.

Please note: In case of acne, chemical exfoliation with fruit acid is the preferred method. In fact, physical exfoliation creates skin micro-lesions that aggravate the inflammation.

• To prevent wrinkles and reduce their appearance:

It is in the dermis that new skin cells multiply to replace those that are eliminated. In addition, the dermis contains fibroblasts that synthesize collagen and elastin fibers as well as hyaluronic acid, which are responsible for the density, elasticity, and firmness of the skin.

However, with age, the structure of these fibroblasts changes. They can no longer synthesize collagen and elastin fibers as well as hyaluronic acid. Thus, the first signs of aging appear with a skin that slackens, a dilation of the pores, wrinkles, as well as spots or an increase in dryness.

Lactic acid in skin care is a key active ingredient that acts against the signs of aging. With a higher molecular weight than glycolic acid, it penetrates less deeply into the epidermis. Although it acts on the surface, lactic acid has the capacity to increase the synthesis of collagen and elastin fibers indirectly. Indeed, under physiological conditions (in an aqueous medium), lactic acid is transformed into pyruvic acid by a deprotonation reaction (loss of a hydrogen). Pyruvic acid being more lipophilic, it penetrates more easily to the epidermis. It thus stimulates the synthesis of collagen and elastin fibers by the fibroblasts. The skin gains in elasticity, density, and firmness.

In addition, lactic acid, which is part of the NMF, maintains good hydration of the stratum corneum thanks to its hygroscopic properties. A good cutaneous hydration makes it possible to reinforce the barrier function and the skin and to avoid the appearance of the wrinkles of dehydration.

• To lighten hyperpigmentation:

Brown spots are due to a localized overproduction of melanin, the pigment responsible for the skin's natural coloring. They vary in size and impact the uniformity of the complexion. They can cause some discomfort in the daily life of the subjects concerned.

Scientific studies have also highlighted the depigmenting properties of lactic acid. In fact, lactic acid inhibits the activity of enzymes involved in the melanogenesis process (the mechanism behind the production of melanin): tyrosinases. The results of the studies prove that the topical application of lactic acid considerably reduces pigmentation spots. However, these studies were carried out on a peel with 82% lactic acid (this is above the authorized concentration in cosmetics which is 10%). The use of lactic acid in high doses requires the intervention of a health professional.

Note: Lactic acid is also used in cosmetics because it is a pH regulator.

In cosmetics, lactic acid is used in serums, creams, lotions and cleansers to make the skin smoother and more radiant. According to the European regulation, it is authorized at a maximum concentration of 10% in cosmetic products. The effectiveness of a lactic acid treatment depends on its concentration and pH. The higher the concentration and the lower the pH, the better the action of lactic acid.

A lactic acid treatment should be applied to the entire face. You can also apply it to the neck to prevent the appearance of wrinkles or dark spots in this area.

Lactic acid is a photosensitizing molecule, which means that it increases the skin's sensitivity to the sun (risk of skin irritation and sunburn). Therefore, use your lactic acid products only in the evening. A broad spectrum sun protection should be applied the next morning.

Lactic acid is a mild acid that is generally well tolerated by all skin types. However, before using a product containing lactic acid, perform a skin tolerance test by applying a few drops of the product to the arm. If you observe a skin reaction, do not use your product on the face.