Abstract: Photoaging represents the primary exogenous contributor to skin aging, triggered by ultraviolet exposure. It compromises skin barrier integrity, disrupts elastic fibers, accelerates collagen breakdown, and intensifies oxidative stress. Collagen hydrolysate shows great potential in addressing photoaging owing to its distinctive bioactivity, favorable safety profile, convenience, and economic viability. This review comprehensively examines the anti-photoaging mechanism of collagen hydrolysate: by modulating critical signaling pathways (transforming growth factor-β (TGF-β), mitogen-activated protein kinase (MAPK), nuclear factor erythroid 2 related factor 2 (Nrf2), and nuclear factor kappa-B (NF-κB)), it promotes extracellular matrix homeostasis, mitigates oxidative stress, inhibits inflammation, diminishes hyperpigmentation, and indirectly regulates the gut-skin axis, thereby counteracting photoaging damage. To overcome technical hurdles in the oral administration of collagen hydrolysate, including extensive gastrointestinal degradation and poor targeting efficacy, we summarize the strategies currently used for enhancing the absorption of collagen hydrolysate, highlighting research advances in co-delivery approaches, polysaccharide-based vehicles, and liposomal systems that enhance collagen hydrolysate bioavailability. In view of the existing research limitations, we give an outlook on future research directions and development trends to provide a theoretical basis for the development of collagen-derived functional foods and their deep application in photoaging prevention and management.

Key words: collagen; digestion and absorption; anti-photoaging mechanism; absorption promotion strategies