A proposal for simplifying the labelling of sunscreens

Area of Science:

• Dermatology
• Photobiology
• Cosmetic Science

Background:

• Sun protection factor (SPF) determination via the in vivo ISO 24444 method exhibits significant experimental variability and uncertainty.
• In vitro methods show potential for accuracy, reproducibility, and correlation with in vivo SPF testing.

Purpose of the Study:

• To address uncertainties in current SPF determination methods.
• To propose a novel binary system for sunscreen labeling, replacing the traditional SPF concept.

Main Methods:

• Evaluation of in vitro methods for accuracy and reproducibility.
• Proposal of a binary classification system based on phototesting (in vivo or in vitro).

Main Results:

• The proposed binary system aims to eliminate uncertainties inherent in both in vivo and in vitro SPF measurements.
• Phototesting, either in vivo or in vitro, would determine product categorization within the binary system.

Conclusions:

• A shift from the SPF concept to a binary labeling system is recommended for more reliable sunscreen protection indication.
• The binary system offers a simplified and potentially more accurate approach to communicating sunscreen efficacy.