In some countries, the concentrations of UV filters are always mentioned but you will see that it is irrelevant.
The Drunk Elephant Umbra Sheer physical contains 20% of zinc oxide and the Colorscience Face Shield 12%, still, the Colorscience is SPF50 and Drunk Elephant SPF30. Both only used Zinc oxide as UV filters.
Sunscreens UV protection (SPF and UVA protection) is dependent on the combination of filters, the concentration of filters, the redundancy of filters, the vehicles for the filters, and the dispersion (aka the rest of the formula).
Combination of filters
In order to protect from the full UV spectrum (UVB, UVAII, UVAI) combination of filters is often required, especially with high SPF. For example, Octinoxate is mainly a UVB filter but if combined with Zinc oxide the sunscreen is a broad spectrum.
Concentration of filters
To achieve higher SPF and UVA protection a higher concentration of filters is often required but if the UV filters are not well dispersed into the formula it won’t help. Also, encapsulation of filters can help to achieve a high SPF with less filters.
Redundancy of filters
Unfortunately, not one UV filter for UVB and UVA provide high SPF and high UVA protection. Several UVB and UVA filters are needed to achieve high protection. The La Roche Posay Ultra cream SPF50+ is an excellent example: SPF50+ UVA-PF 35. To achieve this incredible protection it uses 4 filters for UVB and 4 for UVA protection. Also, the redundancy ensures a stronger and even protection all along the UV spectrum.
Vehicles
The rest of the formula matters a lot for sunscreen formulations. Some solvent for UV filters helps to achieve higher SPF with lower UV concentrations (Diisopropyl Sebacate for example). The solvents are essential to properly « dissolve » some of the UV filters.
Dispersion
Even dispersion of UV filters will lead to higher protection than a poor one (watch my video). A proper dispersion results from the emulsion process, the vehicle used, the encapsulation (or not) of UV filters…
Conclusion
Overall the making of all sunscreens requires a lot of advanced chemistry no matter the marketing claims and that is an excellent thing. Our technology protects our skin from further UV damage and skin cancer.
Watch my video to know more.
Thank you for your time.
Cyrille
