Non-Invasive Depth Profiling of Base Cosmetic Formulations in the Skin Using Handheld Confocal Raman Spectroscopy.

Summary

A handheld confocal Raman spectroscopy system quantified in vivo ceramide kinetics from moisturizers in 40 subjects and showed prolonged stratum corneum retention for ceramide-based creams at 24 hours. CRS measurements strongly correlated with LCMS for ceramide NP (r=0.96), supporting non-invasive, real-time formulation assessment.

Key Findings

• Ceramide-based creams showed longer stratum corneum retention than aqueous-based creams, especially at 24 hours post-application.
• CRS quantification of ceramide NP correlated strongly with LCMS (r=0.96) in a validation subset.
• Handheld CRS provided non-invasive, in vivo depth profiling to assess absorption kinetics of cosmetic formulations.

Clinical Implications

Clinicians and formulators can objectively compare moisturizer performance and tailor recommendations, particularly for atopic dermatitis, by tracking ceramide delivery and retention without biopsies.

Limitations

• LCMS validation subset was small (n=4) and limited to ceramide NP
• Single-site study; long-term clinical outcomes and broader analyte panels were not assessed

Future Directions

Expand validation across ceramide species and lipids, assess inter-device reproducibility, and test clinical utility for guiding therapy in atopic dermatitis and xerosis.