Peg-100 Stearate
Also known as Polyethylene glycol 100 stearate, Polyoxyethylene (100) stearate, PEG-100 monostearate
“CIR Expert Panel says: safe as used in cosmetics.”
PEG-100 STEARATE is a high-molecular-weight nonionic PEG ester emulsifier formed by reacting stearic acid with approximately 100 ethylene oxide units. Its large hydrophilic PEG chain gives it an HLB of approximately 18, making it a highly hydrophilic O/W emulsifier primarily used in moisturizers, lotions, and creams at typical concentrations of 0.5–5%. The CIR Expert Panel assessed PEG stearates as a group in 1983 (JACT 2(7):17-60) and confirmed the finding in 2002 (IJT 24(S1):74-80, 2005), concluding that PEG-100 Stearate is safe as used in cosmetics (Finding=S, no conditions). A 2005 peer-reviewed safety assessment of PEGs and their derivatives (Fruijtier-Pölloth, Toxicology) concurred, noting no safety concern with regard to genotoxicity or carcinogenicity for PEG stearates, and that stearates are safe for use in cosmetics across a wide molecular weight range. The principal safety concern for all ethoxylated ingredients is trace 1,4-dioxane contamination from the manufacturing process; this is addressed by vacuum stripping and is considered in the CIR safety evaluation.
High-HLB (~18) nonionic emulsifier: creates stable, fine-droplet O/W emulsions; widely used as the primary or co-emulsifier in moisturizers and creams
Non-ionic character provides broad compatibility with anionic, cationic, and amphoteric ingredients
Confers a non-greasy, cosmetically elegant skin feel due to the hydrophilic PEG chain
CIR Expert Panel concluded safe as used in cosmetics (Finding=S, no conditions), confirmed in 2002 re-review
1,4-Dioxane is an unavoidable trace byproduct of the ethoxylation process used to manufacture PEG-100 Stearate; it is not listed on the label. Industry standard and SCCS guidance recommend finished product levels below 10 ppm, achievable by vacuum stripping during manufacturing (Fruijtier-Pölloth 2005, PMID 16011869).
A 2022 Drosophila in vivo study found 1,4-dioxane induced genotoxic effects at non-toxic concentrations, underscoring continued concern about 1,4-dioxane residuals as a manufacturing impurity across all ethoxylated cosmetic ingredients.
CIR Quick Reference Table (12/2017, revised 07/2018) — PEG-100 Stearate row: Finding=S, Citation=JACT 2(7):17-60, 1983 confirmed 11/02 IJ…
“PEG-100 Stearate | S | | JACT 2(7):17-60, 1983 confirmed 11/02 IJT 24(S1):74-80, 2005”— QRT-122017revised072018.pdf, p. 83