AllantoinvsCeramides

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.

Ceramides are sphingolipids comprising a sphingoid base (sphingosine or phytosphingosine) amide-linked to a fatty acid—comprising ~50% of stratum corneum lipids. They integrate into the intercellular lipid matrix between corneocytes, forming the lamellar bilayer structure with cholesterol and free fatty acids that limits transepidermal water loss (TEWL). Optimal molar ratio is ~3:1:1 (ceramides:cholesterol:fatty acids). Topical ceramides (NP/3, AP/6-II, EOP/1) fill gaps from barrier damage by surfactants, retinoids, or inflammation. Cholesterol enables lamellar phase formation; fatty acids provide acidic pH for ceramide packing. Products restoring the complete ratio upregulate barrier repair genes (involucrin, filaggrin, transglutaminase) more effectively. Synthesis occurs via serine palmitoyltransferase and ceramide synthase in keratinocytes.