Scientists at UCLA have developed a mineral sunscreen formula that leaves far less of the pale, chalky residue that often discourages people from using sunscreen every day.
Dermatologists have long recommended daily sunscreen use to reduce UV exposure. Excessive UV radiation is the main preventable cause of skin cancer, the most common cancer in the United States.
Despite these risks, many people don’t apply sunscreen regularly. One common complaint is that mineral sunscreens containing zinc oxide can leave a noticeable white or gray film on the skin.
Reforms zinc oxide to reduce white cast
A study led by researchers at UCLA Health Johnson Comprehensive Cancer Center suggests it may be possible to address this problem without creating entirely new chemical compounds. Instead, the researchers changed the physical shape of zinc oxide particles, which are already used in many mineral sunscreens.
The researchers engineered zinc oxide to create microscopic four-armed structures known as tetrapods. According to the researchers, these particles have less of a white cast than traditional zinc oxide formulations and provide stronger protection from harmful UV rays.
The result is ACS Material Lettercould help prevent skin cancer by making mineral sunscreens more appealing and encouraging their regular use by people with different skin tones.
“This is not just about cosmetics,” said Paul S. Weiss, senior author of the study. He holds the University of California Chancellor’s Chair, is a distinguished professor of chemistry and biochemistry, bioengineering, and materials science and engineering at UCLA, and is a researcher at the UCLA Health Johnson Comprehensive Cancer Center. “Improving the appearance of sunscreens so they can be used more consistently could have real implications for preventing skin cancer.”
Why sunscreen appearance matters
The potential benefits may be especially important for people with darker skin. They are less likely to use sunscreen consistently and more likely to be diagnosed with skin cancer at a later stage.
Melanoma, the deadliest type of skin cancer, is less common in people with darker skin, but research shows they are significantly more likely to die from the disease. One reason for this is that melanoma is often discovered later and more difficult to treat.
For lead author AJ Addae, a PhD candidate in chemical biology at UCLA and an entrepreneur in cosmetics science, this study grew out of personal experience.
“I started thinking about this because I was frustrated with how mineral sunscreens looked on my skin,” Ade said. “Much of my motivation comes from my own experiences trying to use mineral sunscreens and dealing with white casts and other unsightly aesthetic issues. That led me to avoid sunscreens altogether. That frustration was the very starting point for this piece.”
Why mineral sunscreen looks whitish
Zinc oxide is widely used in mineral sunscreens because it blocks not only UVA rays, which contribute to skin aging, but also 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 generally recommended for people with sensitive skin, acne-prone skin, rosacea, or those who prefer non-chemical products.
However, standard zinc oxide particles often aggregate into clumps. This reduces the stability of the sunscreen formulation, causing the particles to scatter visible light and creating a white or gray residue, which is especially noticeable on those with darker skin tones.
The UCLA team investigated whether changing the structure of the particles could prevent agglomeration and improve the appearance of sunscreens.
Most zinc oxide used in sunscreens is made up of very small, roughly spherical nanoparticles produced by chemical manufacturing methods. In the new study, researchers looked at much larger particles produced through a patented high-temperature flame process. These particles are shaped like small quadrupeds.
“Due to their structure, these tetrapod-shaped particles have standoffs and form a porous network rather than collapsing into clumps,” Ade said. “They cannot harden and clump together, so they remain evenly distributed within the sunscreen.”
SPF 30 protection and great stability
The researchers compared zinc oxide in the form of tetrapods to traditional zinc oxide nanoparticles commonly used in mineral sunscreens. The quadrupedal formulation offered 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 approximately 30. Its level of protection is similar to that provided by standard mineral sunscreens.
Tetrapod lotion has become more stable over time. They showed little signs of separating or becoming unusually thick.
The most visible improvements concerned how the particles interacted with light. In laboratory experiments and controlled application to the skin, Tetrapod sunscreen produced a warmer appearance closer to natural skin tone. It did not produce the strong white or gray hues seen with traditional zinc oxide.
The researchers achieved this effect without using additional pigments or special coatings to hide the residue.
“When I applied it to my skin, it didn’t leave a white cast like you often see with zinc oxide,” Adae said. “This was the moment I realized it really worked.”
“What surprised us was how rapid the effect was,” added Weiss, who is also a member of the UCLA California NanoSystems Institute and the UCLA Goodman Luskin Microbiome Center. “The first formulation already showed a visible difference.”
From materials science to skin cancer prevention
This sunscreen technology requires additional testing before it is commercially available. Still, the researchers say their findings show how materials science can help address practical barriers to skin cancer prevention.
“The best sunscreens are the ones that people actually use,” Ade says. “If we can make zinc oxide look better on more skin tones without sacrificing protection, we could help more people protect themselves from the sun’s most dangerous effects.”
The researchers are currently collaborating with UCLA Health’s Department of Dermatology, including UCLA Health’s Skin of Color Clinic. They plan to continue their research by investigating how tetrapod particles interact with the skin microbiome for real-world applications.
Important points
- Mineral sunscreens made with zinc oxide usually leave a visible white or chalky layer on the skin.
- UCLA researchers have found that they can reduce this effect by giving zinc oxide particles the shape of a four-armed quadruped.
- In laboratory testing and controlled skin application, Tetrapod’s formula appeared warmer and closer to natural skin tone, rather than producing harsh white or gray tones.
Other authors of the study are Jennifer Uyanga and Adae’s paper co-advisor, UCLA Chemistry Professor Justin Carman, and University of Southern Denmark Professor Yogendra Kumar Mishra.
This research was funded in part by the National Science Foundation, the UCLA Challenge Initiative, and a Sigma Xi IFoRE Grant-in-Aid.
