Propanediol
Also known as 1,3-Propanediol, Propane-1,3-diol, Trimethylene glycol, Zemea
“CIR Expert Panel says: safe as used in cosmetics.”
Propanediol (1,3-propanediol; CAS 504-63-2; C3H8O2) is a small aliphatic diol increasingly used in cosmetic formulations as a solvent, humectant, and viscosity-decreasing agent, typically positioned as a plant-derived (corn-sugar-fermentation) alternative to propylene glycol (1,2-propanediol). The CIR Expert Panel reviewed Propanediol as part of the 2018 Safety Assessment of 10 Alkane Diols as Used in Cosmetics (Final Report, June 13, 2018) and concluded that seven of the ten alkane diols, including Propanediol, are safe in cosmetics in the present practices of use and concentration. The three ingredients excluded from the safe conclusion for insufficient data were 1,4-Butanediol, 2,3-Butanediol, and Octanediol. Propanediol may be prepared by fermentation from corn-derived glucose using a non-pathogenic Escherichia coli K-12 biocatalyst, or by traditional petrochemical routes. Note: the CIR 2018 Quick Reference Table does not list Propanediol as a standalone row because the alkane diols assessment was published after the QRT revision — the alkane diols 2018 final report PDF is the authoritative ingredient-specific source for Propanediol safety.
Plant-derived (corn-sugar-fermentation) humectant and solvent positioned as a sustainable alternative to petrochemical propylene glycol
CIR Expert Panel concluded safe as used in cosmetics (Safety Assessment of Alkane Diols, Final Report June 2018)
Multifunctional: solvent for water-insoluble actives, humectant for hydration, viscosity-decreasing agent for lightweight textures
Commonly used in K-beauty and 'clean beauty' hydrating serums and toners as a non-petrochemical ingredient
- · Not to be confused with 1,4-Butanediol, 2,3-Butanediol, or Octanediol — the three alkane diols excluded from the safe conclusion in the same CIR assessment for insufficient data
As a small aliphatic diol, Propanediol is likely dermally absorbed; the CIR 2018 assessment did not impose concentration limits but relied on oral toxicity, genotoxicity, and irritation data from the broader alkane diols group
CIR Safety Assessment of Alkane Diols as Used in Cosmetics (Final Report, June 13, 2018; Panel Meeting March 5-6, 2018). Propanediol (1,3…
“The Cosmetic Ingredient Review (CIR) Expert Panel assessed the safety of 10 alkane diol ingredients as used in cosmetics. ... concluded that seven alkane diols are safe in cosmetics in the present practices of use and concentration described in this safety assessment, but that the available data are insufficient to make a determination of safety for three ingredients, namely 1,4-Butanediol, 2,3-Butanediol, and Octanediol. [Scope list names Propanediol (1,3-propanediol) as first ingredient; therefore Propanediol is among the seven safe.]”— aldiol032018FR.pdf, Abstract (p. 2)