Phototoxic or Photoprotective?—Advances and Limitations of Titanium (IV) Oxide in Dermal Formulations—A Review

Abstract

The widespread role of titanium (IV) oxide (TiO2) in many industries makes this substance of broad scientific interest. TiO2 can act as both a photoprotector and photocatalyst, and the potential for its role in both applications increases when present in nanometer-sized crystals. Its sunlight-scattering properties are used extensively in sunscreens. Furthermore, attempts have been made to incorporate TiO2 into dermal formulations of photolabile drugs. However, the propensity to generate reactive oxygen species (ROS) rendering this material potentially cytotoxic limits its role. Therefore, modifications of TiO2 nanoparticles (e.g., its polymorphic form, size, shape, and surface modifications) are used in an effort to reduce its photocatalytic effects. This review provides an overview of the potential risks arising from and opportunities presented by the use of TiO2 in skin care formulations.

Ultraviolet Filters for Cosmetic Applications

“…Although it has been included in Annex VI of Regulation No 1223/2009 since 2019, the nano form is much more often found in adult sunscreen products than the micro form, probably because of its more discreet appearance on the skin. The nano-sized titanium dioxide induces lower skin irritability than most organic sunscreens and is less photoreactive [17,143]. However, when titanium dioxide nanoparticles are exposed to UV radiation, there is a possibility of generating reactive oxygen species (ROS) as a result of a photochemical reaction, leading to potential adverse effects [144].…”