Recently, Yanagisawa et al. reported that the transdermal exposure (mimicking skin-barrier dysfunction or defect) of NC/Nga mice to TiO₂ NPs (15, 50, or 100 nm), in combination with allergen, aggravated atopic dermatitis-like lesions through a T-helper type 2 (Th2) dominant immune response. The study also indicated that TiO₂ NPs can play a role in the initiation and/or progression of skin diseases, since histamine was released, even in the absence of allergen.

Stability and darkening:

While the FDA maintains that the regulated use of titanium dioxide is safe, the European Food Safety Authority and some other experts warn of potential, serious health risks.

However, it can cause photosensitivity, which is why it’s often combined with silica or alumina to prevent cell damage.