Hydrating ingredients are used in cosmetic products to keep the product from drying out and to increase moisture content in skin. This hydrating function is generally performed by humectants. These are hygroscopic ingredients, meaning they are able to attract and hold water molecules from the surrounding environment. Simply put, humectants in skincare work by increasing water content in the upper layer of the skin (the stratum corneum).
Humectants replace the skin’s Natural Moisturizing Factor (NMF) that has been washed away or otherwise depleted. They work in the same way as the NMF, and some humectants used in moisturizers are components of the skin NMF themselves, such as sodium PCA. The key function of a humectant is to form hydrogen bonds with molecules of water. Apart from sodium PCA, common humectants used in skincare include glycerine, AHAs (such as lactic acid and glycolic acid), propylene glycol, urea, hyaluronic acid and sorbitol.
A good humectant will retain moisture both over a wide range of humidity conditions (equilibrium hygroscopicity) and for a long time (dynamic hygroscopicity). The most common humectant used in cosmetics is glycerine, which works on several parameters and is pretty much considered the gold standard of humectants. Still, in order to achieve the best effect, different types of humectants are usually combined. In our Face Toner we've teamed ectoin with glycerine and liquorice root, whereas our Face Cream relies on a classical combination of glycerine and sodium PCA. Our Calming and Clarifying Treatment are based on a mix of propanediol, glycerine and ectoin.