What it is
Behentrimonium Methosulfate is a mild cationic (quaternary ammonium) surfactant built on a long behenyl carbon chain and paired with a methosulfate counterion. It is widely used in conditioners and emulsions as a conditioning and antistatic agent and, in combination with fatty alcohols, as an emulsifier that gives creamy, easily spreadable textures. In sunscreens and skincare it contributes to a smooth, soft after-feel and helps stabilize the emulsion.
Safety & warnings
Behentrimonium Methosulfate is regarded as a comparatively mild cationic surfactant and is generally well tolerated in leave-on and rinse-off products at customary use levels. It is not a recognized fragrance allergen and is not typically associated with comedogenicity. Very sensitive individuals may patch test.
Origin & sourcing
Synthetic; manufactured from behenyl-derived feedstock, often originating from plant oils such as rapeseed.
Questions everyone asks
What does BTMS do in a formula?
It conditions, reduces static, and helps emulsify, giving products a smooth, creamy feel.
Is it harsh like some sulfates?
No. Despite the methosulfate counterion it is a mild cationic surfactant, not a harsh cleansing sulfate like SLS.