Encyclopedia · conditioning agent
Behentrimonium methosulfate
The methosulfate salt of the same C22 conditioning ingredient as behentrimonium chloride, slightly weaker in head-to-head lab testing.
What it is
A quaternary ammonium conditioning agent, usually sold blended with cetyl or cetearyl alcohol as a ready-made conditioning wax. The "-25" and "-50" versions name the percentage of active ingredient. It is a cosmetic ingredient.
How it works
The same as behentrimonium chloride: the positive head group binds the negative hair surface and the 22-carbon tail lubricates. In the 2026 Singapore study both beat the shorter-chain cetrimonium chloride and bulky stearalkonium chloride, but the chloride outperformed the methosulfate, "likely due to the chloride counterion's higher mobility". Tham 2026
What the studies show
- In lab tests on hair and silica wafers, the methosulfate worked well and the chloride salt worked better. Neither repaired oxidative damage. Tham 2026
- Only one relevant paper was found.
Side effects and safety
Expect the same irritation profile as other quaternary ammoniums at high levels. We found no hair-specific safety data.
Bottom line
An effective, cheap conditioner base and a fine choice for anyone. The line that it is "gentler" or "more natural" than the chloride is marketing, because the chemistry is the same family. We are only moderately sure, since there is a single comparative study.
Studies 1
Tham HP et al. Electrokinetic analysis reveals common conditioner ingredient interactions with human hair. Int J Cosmet Sci. 2026
Tested: behentrimonium chloride and methosulfate, cetrimonium chloride, stearalkonium chloride
Result: Longer-chain behentrimonium chloride cut wet combing force and deposited best; none reversed oxidative damage.
Read the study ↗Related
- Behentrimonium chlorideA long-chain, positively charged conditioning ingredient that clings to hair and detangles it, with good lab evidence for smoothing and none for repair.
- Cetrimonium chlorideA shorter-chain conditioning ingredient, a bit less effective than the behentrimonium salts but lighter, found in many shampoos, light conditioners and sprays.
- Cetearyl alcoholA waxy blend of cetyl and stearyl alcohols that thickens conditioners and builds the gel that carries the conditioning agent; despite the name, it is not a drying alcohol.
- Cetyl alcoholA 16-carbon fatty alcohol that thickens conditioners and pairs with conditioning surfactants to form the gel; it is not a drying alcohol.
- How conditioner worksRinse-off conditioner coats hair with a positively charged layer that cuts friction and tangling; it does not repair structural damage.