Potassium lactate is the potassium salt of lactic acid. It is mostly used as a preservative and color stabilizer in meat products to extend their shelf life due to its ability to fight bacteria that would otherwise lead to food spoilage. Use levels of potassium lactate for this purpose vary from 1-4.8%.
In skin care, research has shown that potassium lactate can improve the skin's natural moisturizing factor (NMF) by increasing surface hydration. https://www.paulaschoice.com/ingredient-dictionary/ingredient-potassium-lactate.html?q=Potassium%20Lactate&fdid=ingredients