Skin colour typology and suntanning pathways

Area of Science:

• Photobiology
• Dermatology
• Colorimetry

Background:

• Sun product efficacy evaluation relies on clinical and subjective assessments of skin responses to solar radiation.
• Photobiological responses, including tanning and erythema, vary significantly with skin type and melanin content.
• Instrumental, objective skin color measurement is now feasible, fast, and reliable.

Purpose of the Study:

• To define Caucasian skin color domains and establish a skin color classification.
• To objectively track tanning kinetics induced by UVB, UVA, and combined exposures over three weeks.
• To analyze and define tanning pathways and components (erythema, immediate pigmentation, melanization) in the CIE L*a*b* color space.

Main Methods:

• Utilized the CIE L*a*b* color system for instrumental skin color measurement.
• Classified Caucasian skin types into three categories.
• Employed a vectorial method to analyze tanning components and pathways in the 3D L*a*b* color space.

Main Results:

• Differentiated UVB, UVA, and combined UV tanning by intensity, hue, and duration.
• UVA-induced tanning demonstrated significantly greater longevity compared to UVB tanning.
• No significant interaction effect of UVA and UVB on tanning intensity was observed.

Conclusions:

• The study provides a colorimetric framework for interpreting skin phenomena related to UV exposure.
• Developed skin color classification and tanning models offer practical applications for sun product formulation and evaluation.
• Objective colorimetric analysis enhances the understanding of tanning dynamics and durability across different UV exposures.