A physiologically relevant in vitro screening model for predictive assessment of foundation colour shift

Foundation colour shift, defined as the visible darkening or yellowing following application, continues to pose a significant challenge for colour cosmetics and compromises consumer satisfaction. Existing in vitro protocols often rely on unrealistic sebum loads or static premixes, limiting their predictive accuracy. This study aimed to develop a physiologically relevant in vitro model that simulates dynamic sebum secretion and evaluates timing effects across multiple formulations to support predictive assessment of consumer-perceived foundation colour shift.

Three lab-prepared liquid foundations were applied to opacity charts and monitored for 6 hours using DigiEye imaging. Artificial sebum, in an amount approximating typical physiological secretion over 3 hours, was sprayed via a calibrated airbrush at four time points (0 h, 1 h, 3 h and 5 h). Colour shift was quantified using CIE L*a*b* parameters and ΔE_cmc values. The model's predictive utility was evaluated by comparison with consumer panel observations.

The proposed in vitro model exhibited excellent reproducibility, with highly consistent ΔE_cmc trajectories across replicates, and showed strong alignment with consumer perception. Most of the perceptible colour shift occurred during the early drying phase, whereas sebum application, regardless of timing, introduced only minor variations.

This novel airbrush-based in vitro sebum secretion model bridges laboratory precision with consumer relevance, enabling predictive assessment of foundation colour shift under controlled conditions. By revealing the dominant contribution of drying-phase dynamics, it provides actionable guidance for formulation design and offers a cost-effective, scalable screening tool to support early-stage product development and reduce dependence on extensive consumer trials.