Butylene Glycol: What Does This Ingredient on Labels Do?
Arin Editorial · how this is made
When you look at the ingredient list of a skincare product, you'll likely encounter butylene glycol. This clear, slightly viscous liquid is found in everything from cleansers to sunscreens, serums to moisturizers. But it also appears on "avoid" lists on the internet.
What is this ingredient?
Butylene glycol is an alcohol with four carbon atoms. It was first synthesized in 1890 by Dutch chemist Pieter Johannes Dekkers, who called it "tetramethylene glycol". Today it's produced industrially by hydrogenation of 3-hydroxybutanal. In cosmetics, "butylene glycol" usually means butane-1,3-diol, though the name is sometimes used for the closely related butane-2,3-diol.
What does it do?
It works as a humectant: it binds water and helps skin maintain moisture. It's also a good solvent, allowing poorly water-soluble active ingredients to mix into a formula. Its antimicrobial effect can also boost the power of preservatives.
What do safety data say?
In a 1985 report, the Cosmetic Ingredient Review (CIR) panel concluded that butylene glycol is safe as currently used in cosmetics. Animal studies showed low toxicity; human patch tests showed very low irritation, and repeated testing found no evidence of skin sensitization. Laboratory screens looking for estrogen receptor activity found no effect. Genetic damage tests gave mixed results: some experiments saw an effect, others didn't; the Ames test was negative and the overall database assessment was also negative.
Why is it controversial?
Butylene glycol, along with propylene glycol, appears on some "avoid" lists. The claims usually say it's related to antifreeze or that it irritates skin. However, CIR reported that even undiluted, the primary irritation is very low, and repeated testing found no allergic sensitization. These data don't support the warnings.
The Cosmetic Ingredient Review panel has stated that butylene glycol is safe as currently used in cosmetics.
If you see butylene glycol on a label, don't panic. Current safety assessments indicate it doesn't cause problems at the levels used in cosmetic products. Still, if you have very sensitive skin, testing a new product on a small area first is a good habit.
Sources
- Cosmetic Ingredient Review (CIR) - Final Report on the Safety Assessment of Butylene Glycol, 1985 (HERO ID 4941420)
- EPA ToxCast/ToxValDB veritabanları