Visible Light-Induced Pigmentation: Improved In Vivo Methodology for Measuring Efficacy of 30 Products in 9 Randomised Controlled Trials and Correlation With In Vitro Assessment.

Summary

Across nine double-blind RCTs (188 volunteers, 30 tinted products), a refined VL protection factor (pVL-PF) better fit pigmentation kinetics, with VL protection strongly correlating with pigment load. In vitro transmittance reduction robustly predicted in vivo protection, and 24/30 products significantly reduced VL-induced pigmentation using a Bayesian framework to handle inter-individual variability.

Key Findings

• Refined pVL-PF better captured VL-induced pigmentation dynamics across nine double-blind RCTs.
• VL protection level strongly correlated with pigment content; 24/30 products significantly reduced VL-induced pigmentation.
• In vitro transmittance reduction highly predicted in vivo efficacy; Bayesian modeling incorporated kinetic and inter-individual variability.

Clinical Implications

Supports recommending pigmented, well-balanced sunscreens for patients with melasma or postinflammatory hyperpigmentation; in vitro transmittance can screen products before clinical testing. The refined pVL-PF and Bayesian approach could inform labeling and regulatory standards for VL protection.

Limitations

• Monocentric design of individual RCTs; generalizability to diverse skin types and real-world use remains to be confirmed.
• VL exposure protocols and long-term clinical endpoints (e.g., relapse of hyperpigmentation) were not detailed.

Future Directions

Validate pVL-PF thresholds across Fitzpatrick types and conditions like melasma; harmonize VL labeling; expand in vitro-in vivo correlation datasets and evaluate long-term outcomes under real-world use.