A swipe of mineral sunscreen can leave behind more than sun protection. On people with darker skin tones, it may create a white film so noticeable that preventing sun damage suddenly comes with an unwanted cosmetic trade-off.
AJ Addae knew that frustration well. The UCLA chemical biology doctoral candidate had repeatedly watched zinc oxide sunscreen turn chalky against her skin — and eventually began avoiding it altogether.
Now, Addae and her colleagues may have found a way to reduce that familiar white cast. Their study, published in ACS Materials Letters, suggests the solution could come down to changing the ingredient’s microscopic shape.
“I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin,” said Addae in a press release. “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.”
How Researchers Reshaped Zinc Oxide
Zinc oxide is commonly used in mineral sunscreens because it protects against both UVA radiation, which contributes to premature skin aging, and UVB radiation, which causes sunburn.
The sunscreen formula.
(Image Courtesy of Milo Mitchell/UCLA Health)
Conventional zinc oxide particles are generally tiny and round, making it easier for the particles to aggregate into larger clumps, which is what causes the familiar residue.
“[T]he zinc oxide used in sunscreens tends to aggregate due to its non-uniform particle size. These aggregations form large clumps that can scatter visible light very efficiently when spread onto a surface (such as skin), causing you to see a white cast,” Addae explained to Discover.
To combat this, the UCLA team used a patented high-temperature flame process to produce larger, four-armed zinc oxide structures known as tetrapods. Their unusual geometry helps prevent the particles from clumping together and changes how the sunscreen scatters visible light.
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What Benefits Does the New Sunscreen Have?
The researchers used the same zinc oxide concentration in the experimental and conventional sunscreen formulas, allowing them to compare the two directly.
The altered particles still provided substantial ultraviolet protection, producing an SPF of approximately 30. The formulas also showed fewer signs of thickening or separating over time, suggesting the tetrapod particles could help make mineral sunscreen more stable.
The most visible difference appeared on the skin. Rather than creating a stark gray or white layer, the new formulations reflected warmer tones that blended more naturally during laboratory testing and controlled skin applications. That improvement did not require tinted pigments or special particle coatings.
Addae examines the sunscreen.
(Image Courtesy of Milo Mitchell/UCLA Health)
Researchers must complete further safety and real-world testing before the technology can appear in commercial sunscreen.
“Since the publication, I have recently done some testing on interactions of ZnO tetrapod sunscreens with the skin microbiome and we have seen very positive interactions that have good implications for skin health,” Addae told Discover. “I am interested in how we can extend the UVA-protective properties of formulations containing ZnO tetrapods.”
Why Inclusive Sunscreen Could Help Prevent Skin Cancer
Ultraviolet exposure is the leading preventable cause of skin cancer, yet a sunscreen only works when someone is willing to wear it consistently.
Although melanoma is less common in people with darker skin tones, it is often diagnosed at a later stage, when it can be more difficult to treat. Sunscreen products that leave an obvious residue may add another barrier to regular protection.
“It can be a significant barrier because sun protection should not come with aesthetic drawbacks. For those with darker skin tones, white cast can further deter us from sunscreen usage, posing potential healthcare inequities,” Addae told Discover.
By redesigning a familiar ingredient instead of creating an entirely new one, the researchers have shown how material science could make sun protection more wearable — and potentially make cancer prevention more inclusive.
“This was a great reminder that my research has potential for interdisciplinary impact. A lot of research doesn’t make it out of the lab to the general public, so I appreciate how well-received it has been,” Addae concluded in a conversation with Discover.
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
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