Propylene Glycol

At a glance

CAS number

57-55-6

INCI name

Propylene Glycol

Function

humectant, solvent, preservative booster, emollient, viscosity decreasing agent

Typical use level

1%–15%

Solubility

water

Stable pH

3–11

CAS number and synonyms are sourced from PubChem. Function, usage levels, pH and compatibility are AI-assisted formulation guidance — verify against your supplier's technical data sheet and applicable regulations before use.

Also known as

propylene glycol 1,2-propanediol propane-1,2-diol 1,2-Propylene glycol 1,2-dihydroxypropane 2-Hydroxypropanol Isopropylene glycol Dowfrost Sirlene Methylethyl glycol Methylethylene glycol Monopropylene glycol

Compatibility

Works well with:
Glycerin Hyaluronic Acid Niacinamide Parabens Phenoxyethanol Carbomer Xanthan Gum Sodium PCA Urea Allantoin

Use caution with:
Oxidizing Agents Strong Acids Strong Bases

Propylene Glycol is broadly compatible with most cosmetic ingredients and is widely used as a carrier/solvent to help dissolve actives and boost preservative efficacy. It can cause irritation or sensitization at higher concentrations (above ~5-10%) in leave-on products, particularly in sensitive individuals. It is chemically incompatible with strong oxidizing agents, which can cause degradation.

Formulation notes

EU Cosmetics Regulation does not impose a specific leave-on concentration cap, but industry practice limits leave-on use to ≤15% to minimize sensitization risk; rinse-off products may use higher levels. Some consumers self-report sensitivity; patch testing recommended for sensitive skin formulations. Generally recognized as safe by CIR.

Frequently asked questions

Related ingredients

• Butylene GlycolHumectant
• Pentylene GlycolHumectant
• PanthenolHumectant
• Caprylic/Capric TriglycerideEmollient
• Caprylyl GlycolPreservative
• CyclopentasiloxaneEmollient