NMF-replenishing ingredients are those that help to restore the skin’s Natural Moisturizing Factor (NMF). The NMF is primarily composed of free amino acids and various derivatives of these amino acids, for example, PCA, urocanic acid, and inorganic salts, sugars, as well as urea and lactic acid. The role of the NMF is to maintain adequate skin hydration. The NMF can become depleted with age and also from routine exposure to sensitizing ingredients like drying cleansing agents and denatured alcohol. This leads to visibly dry, tight-feeling, flaky skin. By using NMF-replenishing ingredients, such as aminos acids, PCA, and lactic acid, the skin will be better hydrated. Ultimately, these ingredients will help the skin look and feel healthy, smooth, and supple.