In vivo evaluation of sunscreen application by multispectral imaging: A new tool for educating sunscreen users

Area of Science:

• Dermatology
• Photoprotection
• Imaging Science

Background:

• Standard sun protection factor (SPF) testing uses a 2 mg/cm² application dose.
• Real-world sunscreen application by users is typically much lower than the standard dose.

Purpose of the Study:

• To assess a novel multispectral imaging technique for quantifying in vivo sunscreen application.
• To evaluate the efficacy of an application guide in improving sunscreen usage for an SPF 50+ product.

Main Methods:

• Multispectral imaging analyzed reflectance spectra to determine sunscreen dose.
• 26 volunteers applied sunscreen under three conditions: single application, reapplication, and guided application.

Main Results:

• Unguided application averaged 1.04 mg/cm² (single) and 1.23 mg/cm² (reapplication).
• Guided application resulted in 1.45 mg/cm², a ~40% increase.
• Unguided single application showed less uniform sunscreen spreading.

Conclusions:

• Multispectral imaging effectively measures in vivo sunscreen application.
• Standard SPF testing doses exceed typical user application amounts.
• User education via application guides can enhance sunscreen use and improve photoprotection.