Evaluation of Tinted Sunscreens Protection Against Blue Light Using Transmittance Spectroscopy In Vitro Technique

Blue light component of visible light spectrum, between the wavelengths of 400-500 nm, specifically from 415 to 455 nm, known as high energy visible (HEV) light, has the greatest photobiological capability, including biological and cutaneous effects. Currently, there are no regulatory guidelines for assessing sunscreens protection against HEV. In this study, we evaluated the HEV-blocking potential of various tinted sunscreens after blue light irradiation using transmittance spectroscopy in vitro technique.

We compared various commercialized tinted sunscreen formulations with SPF levels ranging from 30 to 50, varying UV filter systems, antioxidant types, and iron oxide (FeO) concentrations to account for different shades. HEV (415-455 nm) transmittance for each sunscreen applied on PMMA plates was measured using an OL756 spectroradiometer, before and after blue light irradiation (200 J/cm²) with solar simulator. The HEV-blocking potential percentage of each formulation was calculated before and after irradiation.

Overall, sunscreens formulated with FeO and both inorganic filters, zinc oxide and titanium dioxide, demonstrated higher HEV absorbance profiles and blocking potential than darker-tinted organic sunscreens or hybrid, where one inorganic UV filter was present. Consistent with prior reports, the HEV absorbance and blocking potential also correlated with the FeO levels.

This study's findings suggest that depending on their formulations, commercialized tinted sunscreens exhibit different levels of blue light protection. Given the relative newness of tinted sunscreens, plus a lack of regulatory standards, there is a need for more research developing methods to measure protection efficacy of products against visible/blue light exposure.