Acetyl tetrapeptisde-5 is a known humectant or hydroscopic moisturizer which helps reduce eye puffiness, improve skin elasticity as well as overall smoothness. This is done by attracting water from deep within in the skin to the outer-most layer of the skin(stratum corneum), taking advantage of this compounds hydroscopic properties (Making Cosmetics). Humectant rich formulas have also been used to treat xerosis (abnormally dry skin) successfully (PubMed). Humectants can also play an important role as emulsifiers within an overall formulation according to the Cosmetics Database.
