UCLA scientists have created a mineral sunscreen formula that leaves far less of the pale, chalky residue that often discourages people from using sun protection every day.
Dermatologists have long recommended daily sunscreen use to reduce exposure to ultraviolet radiation. Too much ultraviolet radiation is the leading preventable cause of skin cancer, which is the most common cancer in the United States.
Despite those risks, many people do not apply sunscreen regularly. One common complaint is that mineral sunscreens containing zinc oxide can leave a noticeable white or gray film on the skin.
Reshaping Zinc Oxide To Reduce White Cast
A study led by researchers at the UCLA Health Jonsson Comprehensive Cancer Center suggests that the problem could be addressed without creating an entirely new chemical ingredient. Instead, the researchers changed the physical shape of the zinc oxide particles already used in many mineral sunscreens.
The team engineered zinc oxide into microscopic four-armed structures known as tetrapods. According to the researchers, these particles provided strong protection against damaging ultraviolet radiation while producing less white cast than conventional zinc oxide formulas.
The results, published in ACS Materials Letters, could support skin cancer prevention by making mineral sunscreen more appealing and encouraging regular use among people with a wider variety 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.”
Why Sunscreen Appearance Matters
The potential benefits may be particularly significant for people with darker skin tones. They are often less likely to use sunscreen consistently and are more likely to receive a skin cancer diagnosis at a later stage.
Although melanoma, the deadliest form of skin cancer, is less common among people with darker skin tones, research indicates that they are considerably more likely to die from the disease. One reason is that melanoma is often discovered later, when treatment becomes more difficult.
For first author AJ Addae, a UCLA chemical biology doctoral candidate and cosmetic science entrepreneur, the research grew out of personal experience.
“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.”
Why Mineral Sunscreens Look Chalky
Zinc oxide is widely used in mineral sunscreen because it blocks UVA rays, which contribute to skin aging, as well as UVB rays, which cause sunburn and increase the risk of skin cancer. The U.S. Food and Drug Administration classifies zinc oxide as safe and effective.
Mineral sunscreens are commonly recommended for people with sensitive skin, acne-prone skin, rosacea or those who prefer non-chemical options.
However, standard zinc oxide particles often gather into clumps. This can make sunscreen formulas less stable and cause the particles to scatter visible light, producing the white or gray residue that is especially noticeable on darker skin tones.
The UCLA team investigated whether changing the particles’ structure could prevent that clumping and improve the sunscreen’s appearance.
Most zinc oxide used in sunscreen consists of very small, roughly spherical nanoparticles produced through chemical manufacturing methods. For the new study, the researchers examined much larger particles created through a patented high-temperature flame process. These particles take the form of 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.”
SPF 30 Protection With Better Stability
The researchers compared the tetrapod-shaped zinc oxide with conventional zinc oxide nanoparticles typically found in mineral sunscreen. The tetrapod formulas delivered several practical advantages.
When the two types of zinc oxide were used at the same concentration, the sunscreen containing tetrapods reached a sun protection factor (SPF) of about 30. That level of protection is similar to what standard mineral sunscreens provide.
The tetrapod lotions also remained more stable as time passed. They showed fewer signs of separating or becoming unusually thick.
The most visible improvement involved how the particles interacted with light. In laboratory experiments and controlled applications on skin, the tetrapod sunscreen produced a warmer appearance that more closely matched natural skin tones. It did not create the same intense white or gray cast associated with conventional zinc oxide.
The researchers achieved this effect without using added pigments or specialized coatings to hide the residue.
“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.”
From Materials Science to Skin Cancer Prevention
The sunscreen technology will require additional testing before it can become commercially available. Still, the researchers say the findings demonstrate how materials science could help address a practical barrier to skin 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 researchers are now collaborating with the UCLA Health department of dermatology, including UCLA Health’s Skin of Color Clinic. They plan to examine how the tetrapod particles interact with the skin microbiome and continue working toward real-world applications.
Key Takeaways
- Mineral sunscreens made with zinc oxide commonly leave a visible white or chalky layer on the skin.
- UCLA researchers found that changing zinc oxide particles into four-armed tetrapod shapes could reduce this effect.
- In laboratory tests and controlled skin applications, the tetrapod formulas appeared warmer and closer to natural skin tones instead of producing a strong white or gray cast.
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.
Leave a comment