Sustainable sunscreen: New study harnesses natural polymer for high-performance cosmetics

A promising breakthrough in sunscreen technology brings the natural ultraviolet-blocking ability of lignin, which comes from plants, one step closer to high-performance use in commercial cosmetics, offering a potential alternative to synthetic sun-blocking ingredients.

Lignin is an organic polymer found in plants and trees whose key characteristic is providing structure to plant cell walls, allowing them to stand upright. In the study, published in the Journal of Bioresources and Bioproducts, scientists modified lignin chemically and physically for improved cosmetic use. The lignin-based sunscreens they produced had an SPF of 42.9, an increase in the SPF performance from previous lignin research, which was below 10 SPF. When loaded with titanium dioxide, the SPF performance increased to 66.2.

The researchers also made a breakthrough in the sunscreen color, meaning lignin-based sunscreens could be produced to match a range of light to dark skin tones.

“Being readily available, cost-effective, non-toxic, safe, and renewable, lignin holds considerable potential as a natural active sunscreen ingredient,” said the authors in the study.

Overcoming natural challenges

Though previous research has shown that lignin is safe for human use and a natural UV-absorber, it has remained challenging to produce an effective lignin-based sunscreen for multiple reasons. First, unmodified lignin has a relatively low SPF value below 10, so the ingredient needs to be modified to improve performance.

An additional challenge is lignin’s natural dark hue. Though effective for sunscreens for people with darker skin tones, researchers have struggled to modify the ingredient for those with lighter skin tones. Lignin is an organic polymer that naturally occurs in plant and tree cells.

The researchers used two methods to modify lignin to improve its UV-absorption ability and lighten the color. First, they created a polymer by grafting methylene bis-benzotriazolyl tetramethylbutylphenol to alkali lignin. This polymer was then turned into very small, submicron spheres and loaded with titanium dioxide, a naturally occurring mineral that can lighten the lignin and improve opacity. The submicron spheres were mixed with facial cream to create a sunscreen for study. Ultimately, the two methods to modify the lignin successfully produced increased sun protection performance. 

“Moreover, the sun protection performance and color stability of the prepared sunscreen sample remain unaltered even after three hours of UV irradiation, exhibiting excellent photostability,” said the authors.

Lignin has the added bonus of being an untapped resource that is widely available and currently a by-product of the pulp industry, a topic covered previously in Personal Care Insights. As a result, this research breakthrough could bring lignin one step closer to being a sustainable, natural UV-blocking ingredient for high-performance sunscreens.

Innova Market Insights data show a 44% average annual growth in plant-based personal care launches since 2018.