UCLA Scientists Develop Mineral Sunscreen Without the Chalky White Cast

By reshaping zinc oxide particles into microscopic four-armed structures, researchers have created an SPF 30 formula that stays invisible on more skin tones.

Mineral sunscreens offer broad protection against both UVA and UVB radiation, but they come with a cosmetic drawback that has frustrated users for decades: a chalky white or gray film that is especially visible on darker skin tones. Now researchers at UCLA Health have found a way to solve that problem without inventing a new chemical ingredient.

The Tetrapod Solution

The key innovation is in the shape of the zinc oxide particles. Conventional mineral sunscreens use tiny, roughly spherical nanoparticles of zinc oxide. These particles tend to clump together, scattering visible light and creating the white cast. The UCLA team, led by Professor Paul S. Weiss and doctoral candidate AJ Addae, engineered much larger particles in the shape of microscopic four-armed structures called tetrapods.

Using a patented high-temperature flame process, the researchers produced zinc oxide tetrapods that do not clump the same way spherical particles do. The result is a sunscreen that blocks ultraviolet radiation as effectively as standard SPF 30 formulas but leaves far less visible residue on the skin. The findings were published in ACS Materials Letters.

Why it matters: Skin cancer is the most common cancer in the United States, and ultraviolet radiation is its leading preventable cause. Yet many people skip sunscreen because of how mineral formulas look and feel — particularly those with darker skin tones, who are more likely to receive a skin cancer diagnosis at a later, more dangerous stage.

A Personal Motivation

For AJ Addae, the research was personal. "I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin," Addae said. "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."

The team's approach addresses a real public health gap. Although melanoma is less common among people with darker skin, they are significantly more likely to die from it, partly because the disease is discovered later. If improving the cosmetic properties of mineral sunscreen leads to more consistent use, the impact on skin cancer prevention could be substantial.

Beyond Appearance

Mineral sunscreens are already recommended for people with sensitive skin, acne, or rosacea, and for those who prefer non-chemical sun protection. The FDA classifies zinc oxide as safe and effective. By removing the main aesthetic barrier to regular use, the tetrapod-shaped zinc oxide could make daily sun protection more accessible across a wider range of skin types and tones. The researchers are now exploring ways to scale up production and bring the formula to market.