What is lactic acid?

Lactic acid is a naturally occurring alpha-hydroxy acid (AHA) found in fermented milk, fruit, and some vegetables. In cosmetics, it is mainly obtained through bacterial fermentation of vegetable sugars, making it compatible with vegan formulas.

It is the most tolerated AHA in its family. Its molecule is larger than that of glycolic acid, it penetrates more slowly and works more gently. Ideal for those new to chemical exfoliation or for skin that does not tolerate other acids well.

How it works on the skin

Lactic acid works by dissolving the bonds that hold dead cells to the skin's surface. By loosening them, it facilitates their natural shedding without the need for scrubbing. The result is finer, more even skin that is more receptive to subsequent active ingredients.

It also has its own humectant action: it is part of the skin's natural moisturizing factors (NMF), which differentiates it from other AHAs. It exfoliates and moisturizes at the same time, without the drying effect that sometimes accompanies more aggressive acids.

Properties and benefits

• Gentle chemical exfoliant, renews the skin surface without friction
• Improves texture and refines visible pores
• Evens out skin tone and reduces superficial spots
• Has its own humectant effect, moisturizes while exfoliating
• Stimulates collagen production with continued use
• More tolerated than glycolic acid, suitable for sensitive skin
• Improves the absorption of subsequently applied active ingredients
• pH balancing in cleansing formulas

Use and integration into routine

In active serums, it is typically used at night, when the skin is not exposed to UV radiation. In facial cleansers, the concentration is low and the contact time is brief, which reduces the risk of irritation and makes it suitable for daily use.

It combines well with hyaluronic acidto compensate for any drying effect, with niacinamideto enhance the effect on spots and pores, and with jojoba oilas a final step to seal in moisture.

Always use sunscreen during the day, especially if used in serums or higher concentrations.

Curiosities and facts

The acid of antiquity
Ancient Egyptian women bathed in fermented milk to keep their skin soft. They knew nothing about AHAs or pH, but the effect was real. Cleopatra is the most cited, although it is probably a legend. What is certain is that sour milk as a cosmetic has been used empirically for millennia. Science later came to explain why it works.

AHA, PHA, BHA: the acid family
AHAs (lactic, glycolic, mandelic acid) act on the surface, ideal for texture, spots, and radiance. BHAs (salicylic acid) are fat-soluble, penetrate the pore, and are better for acne and blackheads. PHAsare the gentlest version of AHAs, even larger molecules, with minimal irritation. Lactic acid is right in the middle: more tolerated than glycolic, more active than PHAs.

Vegetable fermentation
Most cosmetic lactic acid today is produced by fermenting corn, beet, or sugarcane sugars using Lactobacillus bacteria, the same ones that ferment yogurt. The result is chemically identical to dairy-derived lactic acid but 100% vegetable. This is why it appears in vegan cosmetics without contradiction.

This is how it appears in the INCI: Lactic Acid

Other active ingredients you might be interested in

Niacinamide: enhances the effect on blemishes and uneven tone, a very studied combination for evening out the skin.
PHA: the gentlest alternative in the family, ideal if lactic acid is too active for your skin.
Hyaluronic acid: deep hydration that compensates for the renewing effect of lactic acid and strengthens the barrier.
Bakuchiol: a plant-based alternative to retinol, complements the work of lactic acid in anti-aging routines without irritation.