Glycerin, also known as glycerol, is a trihydroxy alcohol renowned for its hygroscopic properties, making it a staple in both skincare and haircare formulations. As a potent humectant, glycerin attracts water molecules from the environment and deeper layers of the skin, thereby enhancing hydration of the stratum corneum. This action not only maintains skin moisture but also fortifies the skin’s barrier function, assisting on the prevention of transepidermal water loss (TEWL). Furthermore, glycerin’s emollient characteristics contribute to skin softness and elasticity, making it beneficial for various skin types, including sensitive and acne-prone skin.​

In haircare, glycerin serves as an effective moisturizer, particularly for dry, coarse, or curly hair types. Its ability to draw moisture into the hair shaft helps in reducing brittleness and breakage, thereby promoting hair strength and resilience. Additionally, glycerin’s conditioning properties smooth the hair cuticle, enhancing shine and reducing frizz. However, it’s noteworthy that in low-humidity environments, glycerin may draw moisture out of the hair, potentially leading to dryness; thus, its use should be tailored to environmental conditions.