What is it?
A thickener made from hydroxyethylcellulose, a cellulose that has been reacted with ethylene oxide, with cetyl groups attached. Cetyl groups are 16-carbon, oil-loving chains. They make the polymer chains cling together, so it thickens and stabilizes creams, lotions and cleansers and helps keep oil and water from separating.
Key information
- Cetyl hydroxyethylcellulose is hydroxyethylcellulose with added cetyl chains, so like its parent it is made with ethylene oxide.
- It works as an associative thickener: its oil-loving side groups link the polymer chains into a thickening network.
- The CIR Expert Panel concluded in its 2009 amended assessment that it is safe as used, at concentrations then reported up to 2 percent.
More information
Cetyl hydroxyethylcellulose is built on hydroxyethylcellulose, which is made by reacting cellulose with ethylene oxide in the presence of sodium hydroxide, a step chemical references describe as an ethoxylation. It also carries cetyl (hexadecyl) groups, the same 16-carbon chain found in cetyl alcohol (see cetearyl alcohol), attached to the cellulose backbone as ethers.
Cosmetic scientists call this kind of polymer a hydrophobically modified hydroxyethylcellulose. When it is concentrated enough, the oil-loving side groups cluster together and link the chains into a network, which is why it is known as an associative thickener. It also interacts with the surfactants in cleansers.
The Cosmetic Ingredient Review (CIR) Expert Panel included cetyl hydroxyethylcellulose in its 2009 amended safety assessment of cellulose and related polymers and concluded that it is safe as used, at concentrations then reported up to 2 percent.
Because it is made from hydroxyethylcellulose, it shares that ingredient’s link to ethylene oxide, the reason we rate ethoxylates Red Light. For a related food-grade cellulose made with ethylene oxide, EU food scientists in 2002 listed ethylene oxide and 1,4-dioxane among possible impurities and accepted it only with strict residue limits. We did not find published measurements of these residues in cosmetic-grade cetyl hydroxyethylcellulose.
Reality check: the CIR found it safe as used, usually at low levels, but it is an ethoxylated ingredient that label cues such as PEG or -eth- won’t flag.
Sources: Cosmetic Ingredient Review: Quick reference table of safety conclusions (2016); PubChem: Hydroxyethyl cellulose; International Journal of Cosmetic Science: Compatibility of personal care thickening polymers in sulphate-free surfactants; European Commission Scientific Committee on Food: Opinion on 1,4-dioxane, 2-chloroethanol and glycol impurities in food additives and ethyl hydroxyethyl cellulose (2002)
