Titanium dioxide has become one of the most popular sunscreen filters in recent years—and it’s easy to see why. As concerns started building around certain chemical sunscreens being absorbed into the bloodstream at levels way above what’s considered safe, the public began to shift toward mineral-based options. Naturally, titanium dioxide saw a huge surge in use.

Now, when we talk about mineral sunscreens, we’re really talking about two players: titanium dioxide and zinc oxide. Between the two, zinc oxide wins hands down in both safety and performance, having lesser white cast than titanium. It gives solid protection across both UVA and UVB. Titanium dioxide? It’s predominantly a UVB blocker, so you’ll usually see it paired with other ingredients to round out that spectrum.

And titanium dioxide doesn’t just show up in sunscreens—it’s in foundations, concealers, and pretty much any makeup that needs to offer good coverage. That’s because it gives excellent opacity and helps with that smooth, even look people want in their base products.

But here’s where it gets a bit tricky. Titanium dioxide is one of those ingredients that can be both friend and foe, depending on how it’s handled. In the right form and formulation, it offers great protection. But it can also be photoreactive—meaning, when hit with UV light, it can produce reactive oxygen species (ROS). These are unstable molecules like hydroxyl radicals and singlet oxygen that can damage DNA, proteins, and lipids.

Inhalation is another point of concern. Regulatory agencies have flagged the potential genotoxic risk of inhaled titanium dioxide nanoparticles. It’s worth noting that titanium dioxide has been classified as a possible human carcinogen (Group 2B) by the International Agency for Research on Cancer (IARC)—but this classification specifically applies to inhalational exposure, not to topical use. That’s why spray sunscreens or aerosolized makeup products containing titanium dioxide are best avoided.

Cosmetically, titanium dioxide is also known for its white cast—especially on deeper skin tones. Nano versions are a workaround to improve transparency and feel, but they’re not without issues. Nano-titanium dioxide isn’t considered reef-safe and, because of their size, these particles may be more biologically reactive—especially if they’re uncoated or poorly formulated. Some early studies suggest that nano-titanium dioxide could potentially harm hair follicles when exposed to sunlight.

To get around the phototoxicity problem, many manufacturers coat titanium dioxide particles with materials like silica, alumina, or zirconia. These coatings reduce ROS formation while keeping the UV-blocking benefits. But coatings come with their own baggage—like the risk of metal ion leaching or interactions with the skin. So, while they help, they’re not a complete get-out-of-jail-free card. And we definitely need more data on how all of this plays out in real-world use.

Bottom line? Titanium dioxide is a solid UVB filter and has earned its place in sunscreen formulations. But it’s not without caveats.

Best practice? Use the non nano form, and skip the sprays.

Titanium dioxide isn’t going anywhere anytime soon. The goal is to use it smartly—balancing its strengths with a close eye on safety.