What it is
Propanediol in cosmetics most often refers to 1,3-propanediol, a colorless, water-miscible diol with the formula CH2(CH2OH)2. It works as a humectant that helps draw and hold moisture, and as a solvent that dissolves other ingredients and improves their delivery in a formula. It is frequently positioned as a more naturally derived alternative to propylene glycol, with a light, non-tacky feel. It can also help boost the effectiveness of preservative systems.
Safety & warnings
Propanediol is generally regarded as a gentle, well-tolerated humectant and solvent and is often chosen as a milder-feeling alternative to propylene glycol. As with any humectant or solvent, very high levels can occasionally contribute to mild irritation in sensitive individuals, but at typical cosmetic use levels it is considered well tolerated.
Origin & sourcing
1,3-Propanediol can be made by petrochemical routes, but the cosmetic grade is commonly bio-based, produced sustainably from corn sugar by fermentation; an engineered E. coli process developed by DuPont Tate & Lyle BioProducts converts glucose into the diol, and some routes instead convert glycerol using bacteria.
History
Bio-based 1,3-propanediol was commercialized by DuPont Tate & Lyle BioProducts, which reached roughly 120,000 tons of production in 2007 using a fermentation process reported to use about 40 percent less energy than conventional routes; the research teams received the American Chemical Society's 2007 Heroes of Chemistry award. The compound is sold for cosmetic use under names including Zemea, with Susterra used for industrial applications.
Questions everyone asks
Is propanediol the same as propylene glycol?
No. Propanediol is usually 1,3-propanediol, a different molecule that is often bio-based and is frequently used as a lighter-feeling alternative to propylene glycol.
What does propanediol do in sunscreen?
It acts as a humectant to help hold moisture and as a solvent that dissolves and helps deliver other ingredients, contributing to the product's feel.
Is propanediol natural?
It can be made from petroleum, but the cosmetic grade is commonly produced by fermenting corn sugar, making it a bio-based ingredient.