Behentrimonium Methosulfate
Also known as BTMS, Docosyltrimethylammonium methyl sulfate, Behentrimonium methyl sulfate
“CIR Expert Panel says: safe as used in cosmetics.”
Behentrimonium Methosulfate (BTMS, CAS 81646-13-1) is a quaternary ammonium cationic conditioner assessed by the CIR Expert Panel as part of the 2012 trimoniums group safety assessment (IJT 31(S3):296-341). The QRT records a Qualified Safe (SQ) finding: safe when formulated to be non-irritating. No product-type or rinse-off restriction was specified beyond the non-irritating formulation qualifier. Post-marketing adverse event data for behentrimonium chloride (the closely related chloride-salt analogue) reported only 0.69 undesirable effects per million units sold over five years, consistent with a low irritation potential for the class at typical use concentrations.
Primary cationic conditioning agent and emulsifier in hair conditioners, leave-on treatments, and hair masks; provides slip, detangling, and antistatic effects
CIR Expert Panel found safe for use in cosmetics when formulated to be non-irritating (SQ, IJT 31(S3):296-341, 2012)
Widely used in natural and clean-beauty formulations as a milder alternative to behentrimonium chloride due to the methosulfate counterion being considered less irritating in some formulations
- · As a cationic quaternary ammonium compound, potential for skin and eye irritation exists if formulated at elevated concentrations without appropriate non-irritating formulation controls
- · The CIR group report covers trimoniums as a class; ingredient-specific clinical data for BTMS specifically are sparse in the published literature
CIR Quick Reference Table (12/2017, revised 07/2018) — Behentrimonium Methosulfate row: Finding=SQ, Citation=IJT 31(S3): 296-341 (2012)
“Behentrimonium Methosulfate | SQ | safe when formulated to be non- irritating | IJT 31(S3): 296-341 (2012)”— QRT-122017revised072018.pdf, p. 11