The white cast problem that keeps people unprotected
Mineral sunscreen works. The problem is that most people stop using it the moment they look in the mirror.
Zinc oxide—the active ingredient in mineral sunscreens—sits on your skin like a layer of chalk. On lighter skin tones it's noticeable. On darker skin tones it's impossible to ignore. So people skip it. And when they skip sunscreen, skin cancer risk climbs. In the U.S., skin cancer is the most commonly diagnosed cancer overall, yet rates of regular sunscreen use remain stubbornly low, especially among people with darker skin, who then face worse outcomes when melanoma does develop.
UCLA researchers just found a surprisingly simple fix: change the shape of the zinc oxide particle itself.
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Start Your News DetoxHow a tetrapod beats a sphere
Traditional zinc oxide particles are tiny, roughly spherical nanoparticles. They pack together tightly in sunscreen formulas—imagine marbles in a jar—which causes them to scatter visible light in a way that creates that telltale white film.
A team led by Paul Weiss at UCLA's Jonsson Comprehensive Cancer Center engineered zinc oxide into a different shape: four-armed structures called tetrapods. Because of their geometry, these particles can't collapse into clumps. They form a loose, porous network instead, staying evenly distributed throughout the sunscreen.
The result, published in ACS Materials Letters, was striking. When formulated at the same concentration as conventional zinc oxide, the tetrapod-based sunscreen achieved an SPF of about 30—standard protection—but reflected light differently. Instead of white or gray, the lotion appeared warmer, closer to natural skin tones, without any added pigments or special coatings.
"When I spread it on my own skin, I didn't get that white cast I usually see with zinc oxide," said AJ Addae, the doctoral candidate who led the work. "That was the moment I realized this could really work."
Addae's motivation was personal. He'd been frustrated by how mineral sunscreen looked on his own skin, which eventually led him to avoid it altogether—the exact opposite of what public health needs.
Why this matters beyond cosmetics
The white cast isn't a vanity issue. It's a barrier to protection.
Research shows that people with darker skin tones use sunscreen less regularly and are diagnosed with melanoma—the deadliest form of skin cancer—at later stages. Though melanoma is less common in darker skin overall, survival rates are significantly lower, largely because the disease has progressed further by the time it's caught. Removing a cosmetic obstacle to daily use could shift that calculus.
"If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention," Weiss said.
Zinc oxide itself is already FDA-approved as safe and effective, and dermatologists recommend it for sensitive skin, acne-prone skin, and anyone preferring non-chemical options. The tetrapod particles maintain all those benefits—the sunscreen was also more stable over time, with less separation or thickening—while solving the visibility problem.
What's next
The team is now working with UCLA Health's Skin of Color Clinic to test how these particles interact with the skin microbiome and move the technology toward actual products. Further testing is needed before it reaches shelves, but the principle is proven: sometimes the best public health innovation isn't a new ingredient—it's rethinking the shape of what already works.
