Propylene Glycol
The short version
A versatile humectant and carrier solvent — common in cake icings, flavor extracts, and e-cigarette liquids.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Manufactured by hydrolysis of propylene oxide (itself from propylene). Food-grade material meets strict purity criteria distinct from the technical-grade used in antifreeze and HVAC. The naming similarity to ethylene glycol (which IS toxic) drives recurring confusion in popular health discourse.
How it's used
Used as a humectant in icings and frozen desserts, a carrier solvent for flavor and color extracts (most natural-flavor concentrates list propylene glycol as the carrier), an anti-foaming agent, and a solvent for fat-soluble vitamins. Also used as a freezing-point depressant in some food-contact refrigeration systems.
Safety profile
ADI of 25 mg/kg body weight. Generally well-tolerated. Metabolized to lactic acid and excreted; very different toxicity profile from ethylene glycol. Caution at high intake for infants (limited metabolic capacity) and for cats (specific feline toxicity, not human).
Physical & chemical properties
Clear, colorless, slightly viscous liquid. Miscible with water and most polar solvents. Slight sweet taste; nearly odorless. Lower viscosity than glycerol.
Regulation worldwide
Permitted in the EU and US with specific maximum levels per food category (most strictly limited in flavoring extracts: typically 1.0–3.0%).
Educational information only. Not medical or dietary advice.