Lactic acid is a milder form of alpha hydroxy acid very well tolerated even by people with very sensitive skin. The function it performs is twofold: it both moisturises and exfoliates at the same time. The size of the molecules of lactic acid is larger than that of glycolic acid, disabling penetration into the deeper layers of the dermis, which makes lactic acid an ideal ingredient for all skin types, but especially sensitive, mature and photodamaged skin that continuously needs gentle “resurfacing” in order to maintain an even tone and firm tonus. In addition, mild acidification of the skin (that is, maintaining the skin in a naturally acidic pH medium) is necessary in order to preserve the function of the hydrolipidic barrier of the cornified layerof the epidermis (source: Wollina U. 2005 Conservative procedures in skin reconstitution Research Gate. 9:1-8)
Lactic acid has been proven to stimulate biosynthesis of the skin’s ceramides which results in superior quality of the skin’s lipid barrier and an increased level of the skin’s resistance to drying out (source: Rawlings A.V., Davies A. at al 1996 Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function Dermatology Research, 288:383–390).
Combined with glycolic acid in lower percentages, AHA products based on lactic acid provide skin with intensive yet non-invasive or very gentle exfoliation, contribute to the skin’s level of hydration, reduce the appearance of shallow wrinkles and fine lines, soften the skin and prep it for application of other active components.
