AllantoinvsGlycerin

Allantoin (5-ureidohydantoin) stimulates cell proliferation and tissue regeneration by promoting fibroblast activity, keratinocyte proliferation, and extracellular matrix synthesis including collagen and glycosaminoglycans. It acts as a mild keratolytic by promoting the natural desquamation process—loosening corneocyte adhesion and facilitating shedding—without the irritation, pH disruption, or barrier compromise associated with alpha- or beta-hydroxy acids. Allantoin has anti-inflammatory properties through modulation of prostaglandin synthesis (inhibiting COX-2 and reducing PGE2) and may downregulate pro-inflammatory cytokines. Its moisturizing effect comes from increasing the water-binding capacity of the extracellular matrix and stratum corneum; it is highly soluble and forms hydrogen bonds with water. Allantoin also promotes wound epithelialization. Its safety profile—non-irritating, non-sensitizing, non-comedogenic—makes it suitable for compromised skin, post-procedure care, and infant formulations.

Glycerin (glycerol) is a small three-carbon polyol (92 Da) that penetrates the stratum corneum via intercellular lipid and transcellular routes. It acts as a humectant through osmotic mechanisms—creating a concentration gradient that draws water from the atmosphere (when humidity >65%) and from deeper epidermal layers. Glycerin upregulates aquaporin-3 (AQP3), a glycerol-permeable water channel in keratinocyte membranes that facilitates water and glycerol transport. It supports the natural moisturizing factor (NMF)—amino acids, lactate, and urea that maintain stratum corneum water-holding capacity. Glycerin modulates keratinocyte differentiation and may enhance lipid lamellae organization. Mild antimicrobial activity occurs through osmotic stress. Clinical studies demonstrate hydration efficacy comparable to or exceeding hyaluronic acid.