What it is
PEG-1540 is a polyethylene glycol with an average molecular weight of approximately 1500 daltons (designated PEG-32 in EU nomenclature, reflecting approximately 32 ethylene oxide repeat units). At room temperature it is a white waxy solid or flake. It is freely soluble in water and compatible with many organic solvents. In cosmetic formulations it acts as a humectant to attract and retain moisture, a binder to hold compressed powders together, and an anti-caking agent to keep dry products free-flowing. It also functions as a solvent and dispersing agent, improving the blending of other ingredients. It is used across bath and shower products, color cosmetics, hair care, skin care, and sun care formulations.
Safety & warnings
The CIR Expert Panel considers PEGs safe for cosmetic use. The primary concern is manufacturing impurities: ethylene oxide and 1,4-dioxane can remain as trace contaminants from the ethylene oxide polymerization process; reputable manufacturers control these to below 1 ppm. EWG flags all PEG ingredients for potential 1,4-dioxane contamination. PEG-1540 should not be applied to damaged or broken skin, as penetration and irritation risk increase on compromised skin barriers. Sensitization on intact skin is rare. Higher-molecular-weight PEGs (above ~1000) have lower dermal penetration than low-MW grades.
Origin & sourcing
PEG-1540 is a synthetic polymer produced by the catalytic polymerization (ring-opening addition) of ethylene oxide onto ethylene glycol or diethylene glycol. The chain length is controlled during manufacture to achieve a target average molecular weight near 1540 g/mol. The CAS number 25322-68-3 covers the full PEG homolog series. The material is purified to remove residual ethylene oxide and 1,4-dioxane before cosmetic use.
History
Polyethylene glycols were first synthesized in the late 19th century and developed commercially in the 1930s by Union Carbide (Carbowax brand). Solid-grade PEGs such as PEG-1540 became widely adopted in pharmaceutical and cosmetic manufacturing through the mid-20th century. The EU CosIng database lists PEG-1540 (as PEG-32) with recognized humectant, binder, and anti-caking functions. The CIR Expert Panel has reviewed PEGs as a class and concluded they are safe for cosmetic use under current conditions.
Questions everyone asks
What is the difference between PEG-1540 and PEG-32?
They are the same ingredient. PEG-32 is the EU INCI name, reflecting the approximate number of ethylene oxide repeat units (~32). PEG-1540 is the Japanese INCI naming convention, which uses the average molecular weight (~1540 g/mol) instead of the repeat-unit count.
What does PEG-1540 do in a sunscreen or moisturizer?
It primarily acts as a humectant to help the formula attract and hold moisture, a binder in pressed or powder products, and a solvent/dispersing agent that improves blending of other ingredients, contributing to a smooth, even texture.
Is PEG-1540 safe for sensitive skin?
PEG-1540 has low acute and chronic toxicity and rarely causes sensitization on intact skin. The main risk is from manufacturing impurities (1,4-dioxane, ethylene oxide), which responsible manufacturers reduce to trace levels.
Why do some ingredient checkers flag PEG-1540?
EWG Skin Deep flags PEGs primarily due to the potential for trace contamination with 1,4-dioxane, a probable carcinogen formed as a byproduct during ethylene oxide polymerization. The ingredient itself has a low hazard score, but impurity risk elevates overall concern ratings on precautionary databa