What defines dry skin? Correlating a range of skin hydration parameters with In Vivo Confocal Raman Spectroscopy

Area of Science:

• Dermatology
• Biophysics
• Optical Spectroscopy

Background:

• Assessing skin hydration is crucial for dermatology and product development.
• Traditional methods for measuring skin hydration lack standardized correlation.
• In vivo Confocal Raman Spectroscopy (ICRS) offers quantitative water concentration profiling within the stratum corneum (SC).

Purpose of the Study:

• To compare electrical, visual, and optical skin hydration measures with water concentration profiles obtained via ICRS.
• To elucidate the relationship between conventional skin hydration assessment techniques and advanced spectroscopic analysis.
• To understand how ICRS data relates to established methods for evaluating skin dryness.

Main Methods:

• Skin hydration was assessed using visual grading, Corneometer®, Visioscan, and ICRS on lower-leg skin.
• Surface capacitance was measured using a custom fingerprint sensor.
• Trans-epidermal water loss (TEWL) was measured using evaporimetry to assess SC barrier function.

Main Results:

• Significant correlations were found between ICRS data and various traditional skin grading and measurement approaches.
• ICRS revealed a distinct, relatively flat water profile near the SC surface in subjects with dry skin.
• Electrical and optical methods showed varying degrees of correlation with ICRS hydration profiles.

Conclusions:

• Quantitative in vivo techniques like ICRS provide valuable insights into conventional skin hydration assessments.
• Traditional and biophysical methods offer unique, complementary information about different SC regions.
• These findings can inform more effective product development strategies for skin hydration and dryness.