Titanium dioxide is a mineral that is commonly found in food coloring, toothpaste, paint, and sunblock. It absorbs UV light at a high capacity, it doesn't break down in the heat of the sun, it's gentle on the skin without leaving white traces and it creates a physical barrier against rays making it a sunblock, not just a sunscreen. Therefore it is often present in SPF for children and those with sensitive skin [1]. Also, since it is encapsulated inside of a silicone molecule, the application is smooth and lightweight.

However, there is controversy surrounding titanium dioxide because of its possible link to cancer in humans [2]. The argument for it is that it still blocks cancer-causing UVA and UVB rays, making it safer to use than nothing at all. For those of you who are looking for a titanium-dioxide free sunscreen until more conclusive evidence is released, check out these options [3].

Source [4]