Lactic Acid, an Acid Suitable for Dry Skin.

Hydroxy acids are widely used in cosmetics. There are different types depending on their chemical structure:

• Alpha-hydroxy acids (A.H.A.) e.g. glycolic acid, lactic acid, mandelic acid, citric acid ... ;

• Beta-hydroxy acids (B.H.A.) e.g. salicylic acid;

• Poly-hydroxy acids (P.H.A.) e.g. gluconolactone.

The common feature of these different acids is their keratolytic effect, i.e. they remove the dead cells on the surface of the skin. This is why it is also called exfoliation. Even though there is a natural process of cell renewal (desquamation), it can be slowed down by various causes. However, there are two main factors that slow down cell renewal: age and excess sebum. Slowed cell renewal can lead to various unpleasant skin symptoms, such as blemishes, a sallow complexion, or the accelerated appearance of signs of aging.

It is therefore essential to support the process of cell renewal, especially with the help of cosmetics based on keratolytic active ingredients such as fruit acids. However, the acid must be carefully selected depending on the skin type.

Dry skin is a skin type characterized by feelings of tightness and irritation throughout the face. These signs are caused by a disruption in the barrier of the skin. The use of highly keratolytic ingredients on dry skin can aggravate the irritation and further refine the skin barrier. This is the case, for example, with glycolic acid. It is an AHA. It is likewise an excellent keratolytic agent that is very well known for fighting skin blemishes and signs of aging. Due to its low molecular weight, glycolic acid penetrates deep into the epidermis and can cause skin irritation.

So if you have dry skin, you'd better turn to lactic acid, which has the advantage of being a gentle exfoliant. Since lactic acid has a higher molecular weight than glycolic acid, it stays on the surface of the skin. This surface action allows it to exfoliate the skin without irritating it. In addition, scientific studies have proven that the application of 5% lactic acid increases the moisture content of the skin. Indeed, lactic acid has the ability to retain water molecules in the epidermis, limiting insensitive water loss. Moreover, it is a molecule that occurs naturally in the skin, as it is part of the natural moisturizing factor (NMF). The fact that it occurs naturally in the skin, contributes to its more gentle effect on the skin.

Note: NMF (or Natural Moisturizing Factor) is composed of amino acids, their derivatives, and extracellular compounds such as lactic acid. Its hygroscopic properties enable it to bind and retain water in the stratum corneum, thus maintaining skin moisture.

Lactic acid is therefore a gentle exfoliant that is ideal for dry skin. It removes dead skin cells and provides smoother, more radiant skin while maintaining the skin's moisture levels.