Moisturizers have various functions in cosmetics, mainly including providing moisture, maintaining the skin's water-oil balance, improving skin elasticity, and promoting the absorption of other active ingredients. Moisturizers solve the problem of dry skin by adsorbing and retaining moisture, while regulating the skin's water-oil balance, making the skin look healthier and smoother. In addition, moisturizers can improve skin elasticity, reduce the appearance of fine lines and wrinkles, and promote the absorption of other active ingredients in cosmetics.

Common moisturizers include glycerin, hyaluronic acid, sorbitol, and adenosine. Glycerin has good hydration and moisturizing properties, capable of absorbing moisture from the air and locking in moisture on the skin's surface; hyaluronic acid is a natural polysaccharide that can form a protective film on the skin's surface to prevent moisture evaporation; sorbitol has excellent antifreeze properties, suitable for use in low-temperature conditions; adenosine can promote skin cell regeneration and repair.

Moisturizers are applied in various forms in cosmetics, including lotions, masks, serums, and creams. Lotions have a lightweight texture, are easily absorbed, and can quickly provide the skin with the moisture and nutrients it needs; masks often contain a high concentration of moisturizers, which can deeply hydrate the skin; the moisturizers in serums can provide moisture deep within the skin and help other active ingredients penetrate and exert their effects better; creams are essential for many people's daily skincare routines, with moisturizers that can lock in moisture for a long time.

The selection criteria for moisturizers include the ability to absorb moisture from the surrounding environment, retain moisture, being colorless, odorless, non-toxic, and having moderate production costs. An ideal moisturizer should be able to retain moisture under general humidity conditions, with the absorbed moisture varying little with relative humidity, and should be colorless, odorless, non-toxic, non-irritating, easily obtainable, and have moderate production costs.