The Challenges of “Shelf Life Stability” in Vitamin C Cosmetics and Ph-Dependent stability strategies

Vitamin C (L-ascorbic acid) is a cornerstone of topical skincare, renowned for its antioxidant efficacy and role in collagen synthesis. While extensive research and development, including water-powder separation technologies, have successfully mitigated the challenge of shelf-life stability, a critical bottleneck persists: inuse stability. This review synthesizes the current body of literature to address this emerging paradigm, focusing on the period after product opening or reconstitution where efficacy rapidly declines. Central to this discussion is the role of pH-dependent stabilization strategies. We critically evaluate and integrate evidence on how pH, concentration, and stabilizers interact dynamically to govern degradation kinetics, antioxidant performance, and cutaneous tolerability during the in-use phase. By mapping these complex interactions and highlighting the existing research gaps—particularly the lack of systematic studies on their synergistic effects—this review aims to consolidate current knowledge and propose a forward-looking framework for designing next-generation vitamin C formulations. The ultimate goal is to shift the industry focus towards ensuring sustained clinical performance throughout the entire product usage lifecycle, thereby guaranteeing that the initial promise of the formulation translates into consistent user benefit.