What is it?
A conditioning ingredient made from guar gum, the thickener ground from the seeds of the guar plant, a legume. The gum is chemically modified with quaternary ammonium groups that give it a positive charge, which helps it stay on hair after rinsing. It reduces static, makes hair easier to comb and thickens formulas. It is used mainly in shampoos, conditioners, body washes and other rinse-off products.
Key information
- The CIR Expert Panel concluded in 2012 that guar hydroxypropyltrimonium chloride is safe as used in cosmetics, where it was reported in 816 products at up to 2 percent.
- The reactive chemicals used to make it are banned as cosmetic ingredients in the European Union; the finished ingredient is not restricted.
- We found no published data on how much of those reactants remains in the finished ingredient.
- It is a very large molecule that is unlikely to be absorbed through the skin.
More information
Guar gum is a galactomannan, a chain of the sugars mannose and galactose stored in the seed of the guar plant. To make guar hydroxypropyltrimonium chloride, manufacturers react the gum with a reactive quaternary ammonium compound: either the epoxide 2,3-epoxypropyltrimethylammonium chloride or its precursor, (3-chloro-2-hydroxypropyl)trimethylammonium chloride.
The Cosmetic Ingredient Review (CIR) Expert Panel assessed it with 15 other guar and related gums and concluded in 2012 that they are safe as used. It was reported in 816 products, 709 of them rinse-off, at up to 2 percent. The Panel judged that these large molecules would probably not be absorbed through the skin to any significant level. Rats tolerated very large single oral doses, and a commercial sample did not cause mutations in a bacterial test. Skin irritation and allergy data came from plain guar gum and hydroxypropyl guar, which the Panel applied to the whole group.
The caveat is how it is made. In 2019 the European Union added both reactants to its list of substances prohibited in cosmetics, which covers chemicals classified as carcinogenic, mutagenic or toxic to reproduction; the epoxide carries the hazard statement “may cause cancer.” The ban applies to the reactants, not to the finished ingredient. The CIR report contains no data on how much reactant remains, and we found none published elsewhere.
On labels it is distinct from hydroxypropyl guar, a related thickener made with a different reactant.
Sources: Cosmetic Ingredient Review: Final report on the safety assessment of galactomannans as used in cosmetics (2012); EUR-Lex: Commission Regulation (EU) 2019/831 adding CMR substances to the list of substances prohibited in cosmetic products; PubChem: Glycidyltrimethylammonium chloride (2,3-epoxypropyltrimethylammonium chloride); European Commission CosIng: Guar hydroxypropyltrimonium chloride
