Glycerin is a component of the skin’s Natural Moisturizing Factor (NMF) that maintain adequate skin hydration. It is a trihydroxy alcohol, which has been included for many years in topical dermatological preparations as a humectant.
Vegetable glycerin is found in soybean, coconut, or palm oil.
Glycerin, also called glycerol.
MOISTURIZING PROPERTIES
Glycerin is a humectant that improves the skin hydration and increase the stratum corneum water content. It is a hydrophilic ingredient due to the presence of the OH groups bonded to water molecules. This structure allows glycerin to attract and bind moisture from the environment to the stratum corneum if the humidity is more than 70%. It also draws moisture from deeper dermis to the epidermis in order to hydrate the skin.
Glycerin allows the skin to retain the moisture by preventing trans-epidermal water loss due to its occlusive effect.
Glycerin is safe to be used in cosmetics based on the concentration specified in this safety assessment.
https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/PRS679.pdf