Titanium dioxide nanoparticles exhibit greater photocatalytic activity than zinc oxide under UV exposure, resulting in increased production of reactive oxygen species that cause damage to collagen and dermal matrix proteins, which requires surface coatings to reduce oxidative stress.

When titanium dioxide nanoparticles on the skin are hit by UV light, they release energy that creates harmful chemicals that break down collagen and other skin support proteins. These chemicals also trigger enzymes that further destroy the skin's structure. Covering the nanoparticles with a thin inert layer stops this process without blocking their ability to reflect UV light.