For years, the biggest complaint about mineral sunscreens has been the ghostly purple or white film they leave behind. While dermatologists often recommend physical blockers, zinc oxide sunscreen remains a consumer favorite, but the white, chalky cast is a drawback for many people with a darker skin tone. AJ Addae, a Black student and innovative scientist who studies chemical biology at UCLA, decided to take a hands-on approach to tackling this problem.
She knew that if people didn’t like how a product looked, they simply wouldn’t use it.
“They leave this white cast on my skin, and it deters me from wanting to use sunscreens,” Addae said.
This aesthetic barrier is more than just a beauty concern; it’s a public health hurdle. It’s an issue people with dark skin have dealt with since zinc oxide sunscreens have been around. Addae knew there had to be an elegant solution that didn’t involve heavy tints or chemical filters. Her goal was to make a product that felt invisible on everyone, regardless of their complexion. “The best sunscreen is one that you’ll wear, and that’s really all where my motivation is for this,” she said.
To get to the root of the issue, she teamed up with her professor, Dr. Paul S. Weiss, at the UCLA Jonsson Comprehensive Cancer Center to understand the problem. Their investigation revealed that the traditional shape of zinc particles was the primary reason for the streaky finish. “We took apart conventional sunscreens that use zinc oxide and learned that the white cast comes from agglomeration of these round, somewhat irregular particles of zinc oxide,” he said.
Essentially, those round particles act like tiny magnets that stick together. The round particles cause the clumping. So what would happen if they could make zinc oxide in a different shape? By switching to a four-armed tetrapod structure, the researchers found the particles would no longer stack into thick, opaque layers.
“The tetrapods have these legs on them that make them stand apart,” Weiss said. The team collaborated with a University of Denmark researcher who had done previous work with tetrapods to perfect the formula. “It forms these networks, really nice, sustained networks of zinc oxide that disperse really well and smoothly and evenly on the skin,” Addae said.
The most important hurdle was ensuring this new shape didn’t sacrifice safety. In their American Chemical Society paper, they proved it did protect the skin just as well as traditional formulas. “We were happy to see that it did absorb really similarly to other zinc oxide types that are on the market,” she said. Additionally, the process is more eco-friendly. Not only was it effective, but Addae also said tetrapod zinc oxide requires no solvent, making it a greener option.
Because zinc oxide is already an approved ingredient, this innovation sidesteps the usual decade-long wait for new sun filters. Scientists said the Food and Drug Administration hasn’t approved a new UV filter since 1999, so getting a new type of sunscreen passed regulators is difficult. This product would already be approved for use.
While chemical sunscreens are available, Addae says many consumers, like herself, prefer zinc oxide. This discovery could finally make daily sun protection a reality for everyone.
“I think it’s going to be a good step in the right direction for getting everyone to wear sunscreen and prevent skin cancer,” she said.
