It is important for people to choose suitable skin care products to moisturize the skin. The compositions of the products for moisture-retention mainly include vitamin B5, PCA sodium, diol, and glycerin. 

Vitamin B5 is mainly used as humectant and softening agent in the skin care products. It can increase the content of hyaluronic acid inside the human skin after it is absorbed by the skin. The security of vitamin B5 has already been proved by various medical researches. It is one of the most popular compositions contained in cosmetics.

PCA sodium is a kind of natural substance existing in the human skin. As a kind of derivant of amino acid, PCA sodium has the relatively high ability of absorbing moisture. It can absorb water from the air and it can also absorb water from the cosmetics for the skin. Its ability of maintaining moisture is much higher than the moisture-retention ability of the traditional wetting agents like glycerin, propylene glycol and sorbic alcohol. In addition, PCA sodium will not stimulate the skin and the eyes. At the same time, it will not block the skin pores.

Butanediol is also a kind of popular composition of the skin care products. It is a kind of micromolecule substance, so the water-catching proportion is low. At the same time, butanediol can help the human body resist the harms caused by bacteria. Therefore, the security is rather high.

Hyaluronic acid is a kind of jelly-like substance existing in the connective tissues and enderonic layer inside the human skin. It is filled with water to maintain the normal elasticity of the skin. The hyaluronic acid can effectively store water for the skin. One gram of hyaluronic acid can even store 500 grams of water. The hyaluronic acid on the market can be divided into two kinds. One is natural, and the other is artificial. The natural hyaluronic acid can be extracted from combs and the artificial hyaluronic acid is synthesized at a low price.

Glycerin also has a high ability of maintaining moisture for the human skin. It can moderately absorb moisture from the air. The single use of glycerin can not realize the ideal effect of moisture-retention. People can make full use of glycerin together with face cream. The face cream can lock water inside the human skin effectively. It can be said that the compositions of moisture-retention must be used suitably to ensure that the effect can be realized to the full extent.