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Scientists report that reshaping zinc oxide particles may reduce the white residue common in mineral sunscreens.
UCLA scientists have created a new mineral sunscreen formula designed to reduce the white, chalky residue that often discourages people from using sun protection every day.
Health experts have long advised applying sunscreen daily to shield skin from ultraviolet radiation. Too much exposure to ultraviolet radiation is the leading preventable cause of skin cancer, which is the most commonly diagnosed cancer in the United States.
Despite these warnings, many people avoid sunscreen because mineral products made with zinc oxide frequently leave a noticeable white cast on the skin.
Rethinking Zinc Oxide for Better Wearability
Researchers at the UCLA Health Jonsson Comprehensive Cancer Center explored whether this cosmetic issue could be solved without introducing a new active ingredient. Their findings suggest that simply changing the physical structure of zinc oxide particles may significantly improve how mineral sunscreen looks and feels on the skin.
In the study, the team engineered zinc oxide into microscopic four-armed shapes known as tetrapods. These uniquely structured particles maintained strong protection against harmful ultraviolet radiation while producing less visible whitening compared with conventional zinc oxide formulas that have long limited broader use.
The results, published in ACS Materials Letters, point to a potential public health benefit. If sunscreen appears more natural on the skin, more people may be willing to apply it consistently, which could help reduce skin cancer risk across a wider range of skin tones.
“This isn’t just about cosmetics,” said senior author of the study Paul S. Weiss, who holds a UC Presidential Chair and is a distinguished professor of chemistry & biochemistry, bioengineering, and materials science & engineering at UCLA and an investigator in the UCLA Health Jonsson Comprehensive Cancer Center. “If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention.”
Disparities in Skin Cancer Outcomes
The potential impact may be particularly meaningful for people with darker skin tones. Research shows they are less likely to use sunscreen regularly and more likely to receive a skin cancer diagnosis at a later stage. Although melanoma, the deadliest form of skin cancer, is less common in people with darker skin tones, research shows they face a significantly higher risk of dying from it, partly because it is often detected later when treatment options are more limited.
For AJ Addae, a UCLA chemical biology doctoral candidate, cosmetic science entrepreneur, and first author of the study, the issue hits close to home.
“I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin,” said Addae. “A lot of my motivation came from my own experience trying to use mineral sunscreen and dealing with the white cast and other unsightly aesthetic issues. This led me to simply avoid sunscreen altogether. That frustration really became the starting point for this work.”
Zinc oxide is widely used in mineral sunscreens because it protects against both UVA rays, which contribute to skin aging, and UVB rays, which cause sunburn and increase the risk of skin cancer. The U.S. Food and Drug Administration classifies it as safe and effective. Dermatologists often recommend mineral sunscreens for people with sensitive skin, acne-prone skin, rosacea, or for those who prefer non-chemical options.
Traditional zinc oxide particles tend to stick together inside sunscreen formulas. This clumping can make products less stable and scatter visible light in a way that leaves behind a white or gray film, an effect that is especially noticeable on darker skin tones.
Engineering a New Particle Shape
To overcome this issue, the researchers decided to look at altering its physical structure to see whether the particle shape made a difference.
Most zinc oxide used in sunscreens is produced through chemical processes that create very small, roughly round nanoparticles. In the new study, the team tested zinc oxide made using a patented high-temperature flame process that produces much larger particles shaped like tiny tetrapods.
“Because of their structure, these tetrapod-shaped particles have standoffs and form porous networks instead of collapsing into clumps,” said Addae. “They can’t pack tightly and aggregate, so they stay evenly distributed in the sunscreen.”
These particles were then compared with conventional zinc oxide nanoparticles commonly used in sunscreens. The team found that sunscreens formulated with the tetrapod-shaped zinc oxide offered several practical benefits.
When formulated into test sunscreens at the same concentration as conventional zinc oxide, the tetrapod-based sunscreen achieved a sun protection factor (SPF) of about 30, which is comparable to standard mineral sunscreens. The lotions also remained more stable over time, with fewer signs of separation or thickening.
Most noticeably, the tetrapod sunscreens reflected visible light differently. Instead of producing a stark white or gray cast, they appeared warmer and closer to natural skin tones in laboratory tests and controlled skin applications, without relying on special coatings or added pigments to mask the white 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.”
“What surprised us was how quickly it worked,” added Weiss, who is also a member of the California NanoSystems Institute at UCLA and the UCLA Goodman-Luskin Microbiome Center. “The very first formulations already showed a visible difference.”
Moving Toward Real-World Use
While further testing is still needed before the technology reaches the market, the researchers say this work highlights a promising direction, one that blends materials science with cancer prevention.
“The best sunscreen is the one people will actually use,” said Addae. “If zinc oxide can be made to look better on more skin tones without sacrificing protection, it could help more people protect themselves from the sun’s most dangerous effects.”
The team is now working with the UCLA Health department of dermatology, particularly with UCLA Health’s Skin of Color Clinic, to study how these particles interact with the skin microbiome and move this closer to real-world use.
Reference: “Flame-Synthesized Zinc Oxide Tetrapods for Photoprotection in Sunscreen Formulations” by Ajoa J. Addae, Jennifer Uyanga, Yogendra Kumar Mishra, Justin Caram and Paul S. Weiss, 26 December 2025, ACS Materials Letters.
DOI: 10.1021/acsmaterialslett.5c01351
The study was funded in part by the National Science Foundation, the Challenge Initiative at UCLA and a Sigma Xi IFoRE Grant-in-Aid.
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