Lactic Acid

Milk is the natural source of lactic acid, but the version used in most skincare today comes from a non dairy fermentation process instead. The result is chemically identical to naturally occurring lactic acid, just easier to formulate with, and it's fully vegan.

As an alpha hydroxy acid, lactic acid exfoliates by loosening the bonds between dead skin cells so they shed the way they would naturally, provided the formula sits at the right pH, generally 3 to 4, and a concentration of 5% to 12%. It doubles as a hydrator too. One of its byproducts, sodium lactate, is actually a natural building block of skin's own moisture holding system.

Its benefits don't stop at exfoliating and hydrating. Lactic acid also encourages the skin to produce more ceramides, which strengthens the barrier, and it appears to support a healthy skin microbiome, in part by interacting positively with Substance P, a neuropeptide involved in how skin signals and recovers from stress. Like glycolic acid, another common AHA, it can also help fade dullness and even out skin tone over time.