Key takeaways
- Mineral sunscreen formulas with zinc oxide often leave a white, chalky cast.
- The new study, led by UCLA researchers, found that a simple change in the shape of zinc oxide particles could address this drawback.
- 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.
UCLA researchers have developed a mineral sunscreen formulation that significantly reduces the white, chalky cast that keeps many people from wearing sun protection daily.
For decades, dermatologists have urged people to apply sunscreen daily to protect against ultraviolet radiation. Excessive exposure to ultraviolet radiation is the leading preventable cause of skin cancer, the most common cancer in the United States.
Yet many Americans still skip it in part because mineral formulas with zinc oxide often leave behind a white, chalky cast.
A new study led by researchers at the UCLA Health Jonsson Comprehensive Cancer Center suggests that these concerns may be fixable without inventing a new chemical ingredient. Instead, a simple change in the shape of zinc oxide particles could help solve one of sunscreen's biggest cosmetic drawbacks.
The researchers report that a newly engineered form of zinc oxide, shaped like microscopic four-armed structures called tetrapods, provides strong protection against harmful ultraviolet radiation while leaving less of the telltale white cast than conventional zinc oxide formulations that have long discouraged regular use.
The findings , published in the journal ACS Materials Letters, could have implications for skin cancer prevention, particularly by encouraging more consistent sunscreen use 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."
Those implications may be especially important for people with darker skin tones, who are often less likely to use sunscreen regularly and more likely to be diagnosed with skin cancer at later stages. While melanoma, the deadliest form of skin cancer, occurs less frequently in people with darker skin tones, research shows they are significantly more likely to die from the disease, in part because it is often detected later, when it is more difficult to treat.
For AJ Addae , a UCLA chemical biology doctoral candidate, cosmetic science entrepreneur and first author of the study, this is extremely personal.
"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 one of the most widely used active ingredients in mineral sunscreens because it blocks both UVA rays, which are linked to skin aging, and UVB rays, which cause sunburns and raise skin cancer risk. It is classified by the U.S. Food and Drug Administration as safe and effective. Mineral sunscreens are often recommended for people with sensitive skin, acne-prone skin, rosacea or those who prefer non-chemical options.
Conventional zinc oxide particles tend to clump together, destabilizing sunscreen formulations and scattering visible light, creating a white or gray residue on the skin that is particularly noticeable on darker skin tones.
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."
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.
Other authors of the study are Jennifer Uyanga and Addae's thesis co-advisor professor Justin Carman of UCLA chemistry, and professor Yogendra Kumar Mishra of the University of Southern Denmark.
The study was funded in part by the National Science Foundation, the Challenge Initiative at UCLA and a Sigma Xi IFoRE Grant-in-Aid.
