In order to evaluate the penetration of the nanoparticles, eight adult male Wistar rats (3 months old) were used for the in vivo experiments. The protocol was approved by the local University Committee for animal testing and is in accordance with the Canadian Council on Animal Care (CICUAL-RD-2021–892-E-UNC-DEC#FCQ).

Tint reducing power, compared with standard samples

Micronized titanium dioxide doesn’t penetrate skin so there’s no need to be concerned about it getting into your body. Even when titanium dioxide nanoparticles are used, the molecular size of the substance used to coat the nanoparticles is large enough to prevent them from penetrating beyond the uppermost layers of skin. This means you’re getting the sun protection titanium dioxide provides with no risk of it causing harm to skin or your body. The coating process improves application, enhances sun protection, and prevents the titanium dioxide from interacting with other ingredients in the presence of sunlight, thus enhancing its stability. It not only makes this ingredient much more pleasant to use for sunscreen, but also improves efficacy and eliminates safety concerns. Common examples of ingredients used to coat titanium dioxide are alumina, dimethicone, silica, and trimethoxy capryl silane.

The evidence also suggests that the toxicity of TiO₂ particles may be reduced when eaten as part of the diet. This is because proteins and other molecules in a person's diet can bind to the TiO₂ particles. This binding alters the physical and chemical properties of the particles, which influences how they interact with cells, tissues and organs.