The sodium salt of lactic acid is hygroscopic and, as a hydrating substance, is part of the skin’s natural moisturizing factor (NMF) along with glycerin, urea, lactic acid, and other organic acids. In addition, sodium lactate forms a buffer system with lactic acid that stabilizes the pH of the skin’s acid mantle at 5.5. It is precisely for these reasons that sodium lactate is also used in cosmetic formulations—namely as a humectant and to stabilize the pH. At a pH of 5.5 and a concentration of 0.5% of 80% lactic acid, approximately 1.7% of 60% sodium lactate should be used.
 
 Usage concentration:
 

 
   1–4%