Behentrimonium chloride

How common

345 of 14,784 products with a full ingredient list in Open Beauty Facts; No. 123 of all the names found on their labels.

What it is

• A “quat” (quaternary ammonium salt): a positively charged head on a 22-carbon tail.

  3 sourcesHide

  Quaternary ammonium salts, including alkyl chain, alkanol, and polymer derivatives (trimoniums)[1] US Cosmetic Ingredient Review expert panel · 2012 · open source

  C 22 -alkyltrimethylammonium chloride Behentrimonium chloride[2] EU law · 2026 · open source

  Conditioner molecules contain cationic surfactant which gives a positive electric charge to the conditioner.[3] Study · 2015 · open source

Why it is in products

• To condition hair and stop static; it also helps mix oil and water. Agents like it are the backbone of a conditioner.

  2 sourcesHide

  commonly used as an antistatic, hair conditioning, emulsifier, or preservative agent in personal care products[4] Study · 2013 · open source

  They are considered the backbone of a conditioner[3] Study · 2015 · open source

What it does

• Its positive charge draws it to hair, which is negatively charged, and most to weathered or damaged areas.

  Well establishedhair2 sourcesHide

  The negative charge of the hair is attracted to the positively charged conditioner molecules, which results in conditioner getting deposited on the hair, especially on areas where there is degree of weathering.[3] Study · 2015 · open source

  electrostatic interaction is the most important one for bleached hair[5] Study · 2023 · open source

• Makes wet hair much easier to comb. In a 2026 lab comparison, its long tail helped it stick and condition better than three other common agents; another lab study measured combing force falling by up to 95% with conditioner gels made from it.

  Good evidencehair3 sourcesHide

  Longer-chain surfactants like BTMC showed superior deposition and conditioning due to stronger van der Waals interactions[6] Study · 2026 · open source

  Wet combing analyses revealed that BTMC significantly reduced combing forces, improving manageability[6] Study · 2026 · open source

  there is an 89% reduction in combing force and a 95% reduction in combing force in the BTAC/CA system of ratio 6:10[7] Study · 2020 · open source

• It does not repair damage. The same study found no reversal of chemical damage: hair is easier to handle, not mended.

  Some evidencehairSourceHide

  ATR-FTIR analysis indicated no reversal of oxidative damage, suggesting conditioners improve manageability without repairing structural damage.[6] Study · 2026 · open source

Downsides and safety

• It can irritate when a product is badly formulated: the US panel’s verdict is safe when formulated not to irritate. A maker’s tests of body lotions with 1 to 5% found no irritation.

  Good evidence2 sourcesHide

  These ingredients were determined to be safe in the present practices of use and concentration when formulated to be nonirritating.[1] US Cosmetic Ingredient Review expert panel · 2012 · open source

  if formulated in appropriate conditions at 1-5%, BTC will not cause dermal irritation or delayed contact sensitization when used in a whole-body, leave-on product[4] Study · 2013 · open source

Where it works

Rules

How much is used

• At most 5% (rinse-off hair) or 3% (leave-on) in the EU.

  SourceHide

  (a) Rinse-off hair products (a) 5,0 % for the individual concentration of behentrimonium chloride[2] EU law · 2026 · open source

Sources

1. Safety assessment of trimoniums as used in cosmetics International journal of toxicology, 2012US Cosmetic Ingredient Review expert panel
2. Regulation (EC) No 1223/2009 on cosmetic products, consolidated text of 18 May 2026 Publications Office of the European Union (EUR-Lex/Cellar), 2026EU law
3. Shampoo and Conditioners: What a Dermatologist Should Know? Indian Journal of Dermatology, 2015Study
4. Confirmation of in vitro and clinical safety assessment of behentrimonium chloride-containing leave-on body lotions using post-marketing adverse event data Cameron DM et al., Toxicology in vitro : an international journal published in association with BIBRA, 2013StudyAuthors include staff of Kao USA
5. Hair surface interactions against different chemical functional groups as a function of environment and hair condition Labarre L et al., International journal of cosmetic science, 2023StudyAuthors include staff of Procter & Gamble
6. Electrokinetic analysis reveals common conditioner ingredient interactions with human hair Tham HP et al., International journal of cosmetic science, 2026StudyAuthors include staff of Ashland and Anton Paar (with A*STAR)
7. Microstructure design of CTAC:FA and BTAC:FA lamellar gels for optimized rheological performance utilizing automated formulation platform Davies AR et al., International journal of cosmetic science, 2020Study
8. Prohibited & Restricted Ingredients in Cosmetics | FDA US Food and Drug Administration

Checked against these sources on 4 November 2026. Spot a mistake? Tell us.