A novel proposal for labelling sunscreens based on compliance and performance

Area of Science:

• Dermatology
• Photoprotection
• Sunsafety

Background:

• Sunscreen efficacy is typically indicated by labeled Sun Protection Factor (SPF).
• Real-world application of sunscreens may not achieve the uniform coverage assumed in standard SPF testing.
• This discrepancy can lead to a significant difference between labeled and delivered photoprotection.

Purpose of the Study:

• To introduce a novel classification system for sunscreens.
• This system integrates the labeled SPF with an objective measure of application compliance.
• The goal is to provide a more realistic assessment of sunscreen performance.

Main Methods:

• Developed an in vitro method to assess sunscreen application uniformity.
• Incorporated an in vivo measurement of applied sunscreen thickness.
• Calculated a 'Compliance Factor' for 10 different sunscreen products.

Main Results:

• Introduced 'SPF(in vivo veritas)' to represent predicted SPF from real-life application.
• Calculated SPF(in vivo veritas) using the Compliance Factor and labeled SPF.
• Identified a significant expected mismatch between labeled and delivered SPF for several tested products.

Conclusions:

• The proposed classification offers a more appropriate measure of delivered photoprotection.
• Consumers can receive better guidance on expected sun protection compared to relying solely on labeled SPF.
• This method enhances consumer understanding and informed sunscreen selection.