In general, moisturizers can be divided into three categories: inorganic, organic, and metal-organic moisturizers. Examples of inorganic moisturizers include calcium chloride; organic moisturizers include polyols, amino acids, and polysaccharides; metal-organic moisturizers include lactates and gluconates. In cosmetics, the moisturizers used are mainly organic moisturizers, which are primarily divided into: polyols, pseudo-natural moisturizing factors, sugars, and others.
Their quality and effectiveness vary; some can only be regarded as simple moisturizing ingredients, while others have skincare benefits in addition to moisturizing.
Polyols
This category of ingredients is easy to obtain, can be produced in large quantities industrially, is inexpensive, and has high safety. The downside is that the moisturizing effect is more easily affected by the humidity of the environment. When the relative humidity of the environment is too low, the ability to retain moisture decreases. Additionally, achieving high-efficiency moisturizing is limited by its own mechanism, making it difficult to achieve. The long-term moisturizing effect is also not ideal.
Common polyols include: glycerin (commonly known as glycerol), butylene glycol, polyethylene glycol (PEG), propylene glycol, 2-Methyl-2,4-pentanediol, xylitol, polypropylene glycol (PPG), sorbitol, etc.
Pseudo-natural moisturizing factors
Natural moisturizing factors (NMF) refer to the moisturizing components contained in the stratum corneum of the skin, which are not a single composition. The main components include amino acids, pyrrolidone carboxylic acid (PCA), sodium lactate, urea, etc. They have hygroscopic properties in the epidermis and stratum corneum, and they regulate the skin's pH, exhibiting excellent skin affinity.
Common pseudo-NMFs include: PCA sodium, sodium lactate, urea, hydroxyethyl urea, etc.
Sugars
Common sugars include: methyl glucose ether, chitosan derivatives, trehalose, tremella polysaccharides, sodium hyaluronate, sugar isomers, etc. Among them, sugar isomers are complexes of sugar isomers derived from wheat D-glucose, and their composition is similar to the endogenous carbohydrates found in NMF in the stratum corneum; sugar isomers bind to the ε-amino group of lysine in keratinocytes, and their unique binding mechanism ensures that active substances are not washed away, continuing to improve skin hydration until the shedding process removes the keratinocytes. Therefore, sugar isomers support the hydration of the stratum corneum and improve mid- to long-term shedding.
Others
Including panthenol, ceramides, natural plant extracts, etc.
Panthenol, also known as vitamin B5, converts to pantothenic acid in the skin and hair. Panthenol exists in the form of pantothenic acid in living tissues and is a key component of coenzyme A, serving as a carrier for acetylation reactions. It can retain moisture for a long time, aids in wound healing, and is a highly permeable humectant and nutrient.