Propylene Glycol
1,2-Propanediol · PG
What it is
A small-molecule diol (CAS 57-55-6) serving as a humectant, solvent, and skin-conditioning agent. Also acts as a penetration enhancer for co-formulated ingredients.
In this product: Humectant, solvent, and penetration enhancer.
Dose & route, what actually matters
Dermal. Measurable skin penetration confirmed in human ex vivo studies. Its significance lies less in its own toxicity profile than in the increased absorption of co-formulated actives it may facilitate.
EUROPEAN UNION
Not listed in EU Cosmetics Regulation Annex II (banned) or Annex III (restricted). CIR Expert Panel concluded PG shows no safety concerns for daily use.
UNITED STATES
Permitted; no FDA restriction. CIR (2017) assessed as safe as a cosmetic ingredient under normal use.
The evidence
CIR Expert Panel (2017): 'PG shows no safety concerns for daily use. PG, along with other 1,2-glycols, was considered to be safe as cosmetic ingredients under normal use practices.'
regulatory · 2017 · source
In a 56-compound human ex vivo skin penetration study, propylene glycol showed measurable dermal penetration and is recognized as a penetration enhancer for co-formulated ingredients.
human · 2019 · source
California Prop 65: Not listed.
How to avoid it
PG is extremely common. If you are using it alongside high-concern actives and want to minimize enhancer effects, choose formulas that list it toward the end of the INCI.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.