Lactic Acid: Which active ingredients should it be combined with?

Lactic acid is a post-biotic obtained by fermenting carbohydrates by microorganisms of the Lactobacillus genus. It was first extracted from milk, hence its name. However, it is not only found in milk. It is present in certain fruits and vegetables, and even in wine. Its use dates back to ancient Egypt. To have soft skin, Cleopatra loved to take baths in donkey milk, which therefore contained a large amount of lactic acid. Today it is found in the composition of many cosmetics such as cleansers, toners, and serums. It is allowed at a maximum concentration of 10% in a cosmetic product according to the European cosmetic regulation.

This interest in lactic acid is based on its exfoliating power. Indeed, lactic acid is an alpha-hydroxy acid (A.H.A.). Like all acids in this family (glycolic acid, tartaric acid, citric acid...), lactic acid possesses keratolytic properties, meaning it eliminates dead cells on the surface of the epidermis by dissolving the intercellular bonds, thus breaking down the lipid cement that binds the cells together. This accelerates skin renewal and combats signs of ageing (wrinkles, fine lines, spots) and imperfections (blackheads, pimples, post-acne spots). Compared to other acids in the A.H.A. family, lactic acid is particularly gentle. This is due to its high molecular weight, which confers a surface action only, unlike other acids that penetrate deeply into the epidermis. Thus, lactic acid is an exfoliant suitable for all skin types, even sensitive ones.

The good tolerance of lactic acid also lies in the fact that it is a molecule naturally present in the skin. Indeed, thanks to its humectant properties, it helps to prevent insensible water loss by retaining water within the epidermis. It is, in fact, part of the Natural Moisturising Factor (NMF) which has the role of improving skin hydration.

Please note: the NMF or Natural Moisturising Factor accounts for 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.

At high concentrations (beyond 10%), in medical peels, lactic acid exhibits depigmenting and brightening properties.

In order to fully benefit from the virtues of lactic acid, combinations with other active ingredients are documented in scientific literature.

Lactic acid can be combined with other active ingredients to enhance its effects. Lactic acid can be paired with:

• Ferulic Acid.

Ferulic acid is a antioxidant agent that combats cell oxidation and thus fights against the photo-ageing of the skin.

A scientific study compared the effectiveness of a peel combining lactic acid and ferulic acid to a peel containing only ferulic acid. The results show a greater effectiveness of the peel combining lactic acid and ferulic acid on fine lines, photo-ageing and hyperpigmentation spots. Indeed, lactic acid being a keratolytic agent, it refines the epidermis by eliminating dead cells. This leads to a better penetration of ferulic acid thus multiplying its effects. Therefore, lactic acid and ferulic acid work synergistically on photo-ageing.

In your beauty routine, on clean and dry skin, use our gentle peeling serum followed by our antioxidant serum containing 3% ferulic acid. As lactic acid is photosensitising, this combination should be used only in the evening.

• Retinol.

The retinol, a derivative of vitamin A, is a potent firming agent that smooths the skin texture, reduces signs of ageing, and effectively combats pigmentation spots and blemishes.

Lactic acid and retinol alleviate acne through their keratolytic actions. A scientific study proves that the topical combination of A.H.A. (including lactic acid), retinol, and B.H.A. (salicylic acid) significantly reduces both inflammatory and non-inflammatory acne lesions within 4 weeks. An overall improvement in skin quality was also observed. This combination is beneficial for acne-prone skin, however, it is not recommended for dry, sensitive, or atopic skin.

In this study, the serum used is a combination of 0.1% of an AHA-Retinol complex, 2% salicylic acid and 10.04% lactic acid.

In order to benefit from the virtues of lactic acid and retinol on acne, use our gentle peeling serum followed by our retinol serum. The combination of these two serums should be applied only in the evening as retinol and lactic acid are photosensitising molecules.

However, the retinol is a molecule that can prove to be irritating and drying. If you have sensitive skin, you should rather turn to the bakuchiol which is a natural alternative to retinol with fewer side effects.

• The other acids.

The combination of lactic acid, which is an A.H.A., with other acids such as B.H.A.s or P.H.A.s can be very beneficial due to their complementary actions. Indeed, lactic acid works on the surface of the epidermis by eliminating dead cells. Our peeling mask with 10% A.H.A. and 10% P.H.A. thus helps to unclog pores while reducing the appearance of imperfections such as blackheads over time. Lactic acid also has humectant properties that improve skin hydration. Salicylic acid, due to its affinity for sebum, penetrates and unclogs the pores of the skin.

Thus, the combination of lactic acid and salicylic acid is also beneficial for acne-prone skin as it provides a comprehensive action against blemishes.

Please note : our local imperfection serum contains 2% salicylic acid and our gentle peeling serum is formulated with 10% lactic acid. In cosmetics, the combination of AHA+BHA should not exceed 10%, therefore the combination of our two serums is not possible.

The combination of A.H.A.s is also highly beneficial. In addition to their shared exfoliating properties, some molecules offer other benefits. For instance, lactic acid not only exfoliates but also has moisturising and soothing properties. Furthermore, the mode of action of A.H.A.s also varies according to their size. Lactic acid, due to its molecular weight, acts on the surface, while glycolic acid, being smaller, penetrates more deeply, stimulating the synthesis of collagen fibres, elastin and hyaluronic acid.

Therefore, combining A.H.A.s allows for a complementary action and increased effectiveness.

Note : Regarding our A.H.A. based serums, these are too highly concentrated to be combined with each other. However, it is possible to find several A.H.A.s in the same cosmetic product, in which case, the dosage will be adjusted accordingly.

Please note : if you have sensitive or atopic skin, we advise against these combinations of acids.