Natural photoprotection under scrutiny: an in vitro evaluation

Area of Science:

• Cosmetic Science
• Dermatology
• Photoprotection Research

Background:

• Growing consumer demand for "natural" cosmetic products extends to sunscreens.
• Plant-derived oils and extracts are marketed as natural alternatives to synthetic UV filters.
• Concerns exist regarding the actual photoprotective efficacy and safety of these natural ingredients.

Purpose of the Study:

• To evaluate the in vitro photoprotective efficacy of eleven plant oils and nine "natural" cosmetic products.
• To compare the performance of natural ingredients against conventional UV filters.
• To assess the need for standardized testing in natural sun protection products.

Main Methods:

• Standardized application of plant oils and cosmetic products onto polymethyl methacrylate (PMMA) plates.
• Measurement of absorbance spectra using an SPF Analyzer.
• Calculation of in vitro sun protection factor (SPF) and in vitro UVA protection factor (UVA PF) values, including photostability testing.

Main Results:

• Most plant oils demonstrated negligible in vitro SPF and UVA PF, with tamanu oil showing limited efficacy that decreased post-photostability.
• Tested "natural" cosmetic products, even those with declared SPF 25-50, showed variable and often insufficient protection.
• Products relying on inorganic filters like titanium dioxide had mixed results, with some offering high SPF but low UVA protection.

Conclusions:

• Plant oils are inadequate for effective photoprotection and cannot substitute conventional UV filters.
• Consumers using natural products may face risks from insufficient UV protection, potentially impacting dermatological treatments.
• Standardized in vitro testing is crucial for accurate product labeling and ensuring reliable consumer protection against UV radiation.