The Index · Glycol humectant / solvent
Propanediol
Propanediol
Bio-based 1,3-propanediol humectant and solvent; lighter feel than butylene glycol for many formulas.
FunctionalFunctional ingredient, not graded for skin benefits
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Propanediol (typically 1,3-propanediol) is a multifunctional glycol used as a humectant, solvent, and sensory modifier. CIR has assessed related propylene glycol family members; 1,3-propanediol is widely used as a gentler-feeling alternative to butylene GlycolFunctional in modern formulas[1].
What it does
Draws water, helps dissolve actives, and can boost preservative efficacy in leave-ons.
The evidence
Safety and humectant function are well established for cosmetic glycols; it is not an active like niacinamide[1].
How to use it
Ubiquitous supporting ingredient — expect it mid-to-high on INCI lists.
What it does in the formula
Functional ingredient — not graded for skin benefits
Humectant and solvent that improves skin feel[1]
Safety & limits
Source and region, always
all — Widely used glycol; generally low irritation vs older solvents at typical use levels.[1] CA US EU UK
Sources · 1
Numbered as cited in the text
- [1]Cosmetic Ingredient Review. Safety Assessment of Propylene Glycol, Tripropylene Glycol, and PPGs as Used in Cosmetics (context for related glycols). CIR (2012)regulator
Revision history
18 Sept 2026Drafted by botTheSkindex Desk