In 2017, French researchers from the Institut National de la Recherche Agronomique (INRAE) were among the first to examine the effects of E171 nanoparticles on the body. They fed rats a dose of 10mg of E171 per kilogram of body weight per day, which was similar to human exposure in food. The research, which was published in Scientific Reports, showed that E171 was able to traverse the intestinal barrier, pass into the bloodstream, and reach other areas of the body in rats. Researchers also found a link between immune system disorders and the absorption of titanium dioxide nanoparticles. 

Titanium dioxide is typically micronized and coated for use in cosmetics products. The micronizing makes this somewhat heavy-feeling ingredient easier to spread on skin, plus a bit more cosmetically elegant. Micronized titanium dioxide is much more stable and can provide better sun protection than non-micronized titanium dioxide.

EFSA Scientific Conclusion on E171