For decades, dermatologists have urged daily sunscreen use to shield skin from ultraviolet radiation, the leading preventable cause of skin cancer, the most common cancer in the United States.
Yet many still hesitate. Why?
Mineral sunscreens, especially those with zinc oxide, often leave behind a white, chalky layer on the skin. It can feel like wearing a ghostly mask, making faces look more like statues than sun‑safe humans. This ‘white cast’ is one of the biggest reasons people avoid sunscreen, even though the protection it provides is priceless.
A new study from UCLA Health suggests sunscreen’s ghostly problem might be solved without inventing anything new. Instead of developing a new chemical, scientists found that simply reshaping zinc oxide particles could make mineral sunscreens less like face paint and more like invisible armor.
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Zinc oxide is the workhorse of mineral sunscreens; it shields against both UVA rays, which age the skin, and UVB rays, which burn it. But there’s a catch: traditional zinc oxide particles clump together, making sunscreen unstable and scattering visible light, resulting in a stubborn white or gray cast.
To tackle this, scientists asked a simple question: what if the problem isn’t the ingredient itself, but its shape? By rethinking the physical structure of zinc oxide particles, they set out to see if a new form could protect without painting.
Scientists have developed a smarter mineral sunscreen. Instead of the old chalky zinc oxide, they’ve reshaped it into microscopic four-armed “tetrapods.” These tiny structures still block ultraviolet rays powerfully, but they leave behind far less of the ghostly white cast that has kept many people from using sunscreen every day.
Senior author of the study, Paul S. Weiss, said, “This isn’t just about cosmetics. If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention.”
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For AJ Addae, a UCLA chemical biology PhD student and cosmetic science entrepreneur, the sunscreen problem isn’t just academic, it’s personal.
“I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin,” Addae explained.
The chalky white cast was so discouraging that she often skipped sunscreen altogether. That frustration became the spark for her research, driving her to reimagine zinc oxide so it could protect without painting.
Most sunscreens use tiny, round zinc oxide nanoparticles. In this study, researchers tested a new approach: a patented flame-based process that produces larger, four‑armed “tetrapod” particles. Because of their shape, these tetrapods don’t clump together; they form airy networks that stay evenly spread in sunscreen.
Compared with conventional zinc oxide, the tetrapod version delivered clear practical benefits, including smoother application and less chalky white cast.
When tested at the same concentration as regular zinc oxide, the tetrapod-based sunscreen reached an SPF of about 30, right in line with standard mineral sunscreens. But it held up better over time, remaining smooth and stable rather than separating or thickening.
Most strikingly, the tetrapod sunscreens reflected light more softly. Instead of leaving a stark white or gray film, they appeared warmer and closer to natural skin tones in lab and skin tests, without needing extra coatings or pigments to hide the cast.
“When I spread it on my own skin, I didn’t get that white cast I usually see with zinc oxide,” said Addae. “That was the moment I realized this could really work.”
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The work isn’t ready for store shelves just yet; more testing is still needed. But researchers say this approach points to an exciting future in which materials science meets cancer prevention. By reshaping zinc oxide, they’ve opened the door to sunscreens that provide powerful protection and look natural on skin.
Journal Reference:
Ajoa J. Addae, Jennifer Uyanga, Yogendra Kumar Mishra, Justin Caram, and Paul S. Weiss. Flame-Synthesized Zinc Oxide Tetrapods for Photoprotection in Sunscreen Formulations. ACS Materials Letters. DOI: 10.1021/acsmaterialslett.5c01351