When and how often should lactic acid be used?

Thelactic acid is part of the alpha-hydroxy acids (A.H.A.) family. Naturally present in the skin, it is produced by the beneficial bacteria of the skin flora. Thus, it is referred to as apost-biotic. Furthermore, this substance can also be found in certain foods such as sugar cane and wine.

Many cosmetic products are formulated with lactic acid, including serums, tonics, and creams. This active ingredient is highly valued primarily for its keratolytic properties. Indeed, lactic acid eliminates dead cells on the surface of the epidermis, accelerating cell renewal. Thanks to its properties, lactic acid is an excellent active ingredient to combat signs of ageing (wrinkles, fine lines) and imperfections (acne, blackheads, post-acne spots). In addition to its exfoliating power, lactic acid maintains good hydration of the horny layer due to its hygroscopic properties. Furthermore, scientific studies have also highlighted the depigmenting properties of lactic acid. Indeed, lactic acid inhibits the activity of enzymes involved in the process of melanogenesis (the mechanism responsible for the production of melanin): the tyrosinases.

Compared to other molecules in the A.H.A. family, particularly glycolic acid, thelactic acid has a gentle exfoliating power. Unlike glycolic acid, which penetrates deeply into the epidermis and can cause irritation, thelactic acid acts on the surface. This is due to its higher molecular weight, which prevents it from crossing the epidermis. Furthermore, as lactic acid is a molecule naturally present on the skin, at the level of the Natural Moisturising Factor (NMF), it is better tolerated by the skin.

Thus, lactic acid is a gentle exfoliant suitable for all skin types, even the most sensitive. It helps to accelerate cell renewal while maintaining good hydration of the epidermis.

Lactic acid is a photosensitising molecule, meaning it increases the skin's sensitivity to UV rays. Therefore, to avoid the risk of sunburn or irritation, a lactic acid treatment should be used only in the evening. Moreover, it is in the evening when cellular regeneration is at its peak (between 11pm and 2am). Make sure to apply a broad-spectrum sunscreen the following morning to protect yourself from the sun's UV rays.

A lactic acid treatment is typically usedonce a day, preferably in the evening. Initial uses may cause slight redness. This is simply the time needed for the skin to get accustomed to the molecule. These effects will fade after several uses. If the redness is too severe, it is recommended to space out its use by a few days until the skin adjusts, or even to stop using lactic acid treatments altogether.

You can incorporate this active ingredient into your evening beauty routine,daily. There is no maximum usage duration to adhere to, as this acid is gentle and generally well tolerated by all skin types.

At Typology, we have formulated a gentle peeling serum containing 10% lactic acid. It helps to remove dead skin cells, revealing smoother, brighter and more even skin. It also containsacerola extract which helps to combat free radicals responsible for dull complexion. Apply 3 to 4 drops of your lactic acid serum to the face, only in the evening. Be sure not to use it in the morning and not to expose yourself to the sun after application. Limit any exposure for a week after application. The use of a broad-spectrum sunscreen is highly recommended. We recommend using your serum for a period of at least 4 weeks in order to observe its effects.

You can also use our peeling mask, enriched with 10% A.H.A. and 10% P.H.A. This concentrated gel mask eliminates dead cells to unclog pores and refine skin texture. It leaves the complexion even and the skin's texture smoothed. Over time, it also helps to reduce the presence of blackheads. Just like our gentle peeling serum, use this mask only in the evening and limit sun exposure in the following days.

• SMITH W. P. & al. Epidermal and dermal effects of topical lactic acid. Journal of the American Academy of Dermatology (1996).

• Rotsztejn H. & al. Lactic and Lactobionic Acids as Typical Moisturising Compounds. International Journal of Dermatology (2018)