Behentrimonium Methosulfate (BTMS-50)

General Description and Role

Claim: “Behentrimonium Methosulfate (BTMS-50) is a cationic emulsifying wax and quaternary ammonium salt derived from rapeseed oil (also known as colza oil), commonly used as a conditioning agent, emulsifier, and thickener in cosmetic formulations. The BTMS-50 variant typically consists of 50% active Behentrimonium Methosulfate blended with 50% cetearyl alcohol (a mixture of cetyl and stearyl alcohols) or cetyl alcohol, and sometimes includes butylene glycol for improved solubility and performance. It is prized in hair and skincare products for its ability to soften, detangle, moisturize, and stabilize emulsions by binding positively charged ions to negatively charged surfaces like hair or skin, while also providing antistatic and hydrating properties.”
Verification: Accurate. Behentrimonium Methosulfate (BTMS-50) is a quaternary ammonium compound derived from rapeseed oil, functioning as a conditioning agent, emulsifier, and antistatic agent in cosmetics. The BTMS-50 form is often a blend of approximately 50% active ingredient with fatty alcohols like cetearyl alcohol, and optionally butylene glycol, enhancing its use in emulsions for skin and hair care by providing softening, moisturizing, and stabilizing effects through cationic binding.
Citations:
- Cosmetic Ingredient Review Expert Panel. (2012). Safety Assessment of Trimoniums as Used in Cosmetics. International Journal of Toxicology, 31(6_suppl), 296-341. https://journals.sagepub.com/doi/pdf/10.1177/1091581812460408
  - “Behentrimonium methosulfate is a quaternary ammonium salt… functions as an antistatic agent and hair-conditioning agent in cosmetics.”
- (2024). What is Behentrimonium Methosulfate? https://photozyme.com/blogs/news/behentrimonium-methosulfate
  - “Behentrimonium Methosulfate plays a crucial role in skincare formulations, offering conditioning, emulsifying, and moisturizing benefits.”

Composition and Production

Claim: “Behentrimonium Methosulfate (BTMS-50) is a quaternary ammonium salt derived from rapeseed oil (also known as colza oil), where erucic acid is extracted, hydrogenated, and chemically reacted to form the compound; the BTMS-50 formulation typically consists of 50% active Behentrimonium Methosulfate blended with 50% cetearyl alcohol (a mix of cetyl and stearyl alcohols) and, in some versions, butylene glycol for enhanced solubility and conditioning.
Overall Formulation: BTMS-50 is typically a 50/50 blend of the active ingredient Behentrimonium Methosulfate and cetearyl alcohol, creating a cationic emulsifying wax in pastille form for use in cosmetics; some variations include 1-3% butylene glycol for improved solubility, with active content ranging from 48-51% Behentrimonium Methosulfate and 49-52% fatty alcohols.
50% Active Behentrimonium Methosulfate: Chemical Structure: A quaternary ammonium salt with the molecular formula C26H57NO4S (or C25H54N·CH3O4S), specifically N,N,N-trimethyl-1-docosanaminium methosulfate, featuring a long C22 carbon chain for conditioning properties.
Derivation Process: Extracted from rapeseed oil (Brassica napus, native to Europe and Asia); erucic acid (C22 unsaturated fatty acid) is isolated, hydrogenated to form saturated behenic acid, then reacted with trimethylamine and dimethyl sulfate (or methosulfuric acid) to create the quaternary compound.
Role in Blend: Provides the primary cationic charge for emulsification, conditioning, and anti-static effects, making it the “active” component that binds to negatively charged surfaces like skin or hair.
50% Cetearyl Alcohol: Chemical Composition: A mixture of fatty alcohols, typically 25-35% cetyl alcohol (hexadecan-1-ol, C16H34O) and 60-75% stearyl alcohol (octadecan-1-ol, C18H38O), with an overall formula around C34H72O2; some BTMS-50 variants use primarily cetyl alcohol instead of the full cetearyl blend.
Derivation Process: Sourced from vegetable oils like palm kernel oil or coconut oil; fatty acids (palmitic for cetyl, stearic for stearyl) are liberated through transesterification or hydrolysis, distilled, and then hydrogenated (reduced) to form the alcohols; often RSPO-certified for sustainability.
Role in Blend: Acts as a co-emulsifier, thickener, and stabilizer, enhancing the texture and stability of emulsions while providing emollient properties without the cationic charge.
Optional Additives (in Some Versions): Includes butylene glycol (C4H10O2, 1-3%) derived from petrochemical or fermentation processes, added to improve solubility, reduce viscosity, and enhance the conditioning feel; not present in all formulations, such as glycol-free versions.”
Verification: Accurate. BTMS-50 is composed of roughly 50% behentrimonium methosulfate (C26H57NO4S), a quaternary ammonium salt with a C22 chain, derived from rapeseed oil via extraction of erucic acid, hydrogenation to behenic acid, and quaternization with trimethylamine and dimethyl sulfate. It is blended with 50% cetearyl alcohol (mixture of C16 and C18 fatty alcohols from vegetable oils) for emulsification and stability, with optional butylene glycol (1-3%) for solubility. This creates a pastille-form wax used in cosmetics for its cationic properties.
Citations:
- Cosmetic Ingredient Review Expert Panel. (2012). Safety Assessment of Trimoniums as Used in Cosmetics. International Journal of Toxicology, 31(6_suppl), 296-341. https://journals.sagepub.com/doi/pdf/10.1177/1091581812460408
  - “The synthesis of behentrimonium methosulfate is representative… by reacting N,N-dimethyldocosan-1-amine with dimethyl sulfate.”
- Holistic Enchilada. (n.d.). How Behentrimonium Methosulfate Measures Up: The Good & the Bad. https://holisticenchilada.com/behentrimonium-methosulfate/
  - “BTMS is a non sulfate ingredient derived from rapeseed oil…”

Skin Type Suitability

Claim: “BTMS-50 is best suited for dry, mature, or normal skin types in skincare due to its moisturizing and conditioning effects:
Dry/Dehydrated Skin: Provides deep conditioning and moisture retention without feeling heavy.
Mature skin: Helps soften and smooth, supporting elasticity in aging skin.
Normal skin: Enhances overall texture and feel without causing imbalance.
Sensitive skin: Generally gentle and non-irritating when used in appropriate concentrations.
Avoid: Acne-prone/oily skin, or young skin (especially under 30), as it may contribute to breakouts or skin issues.”
Verification: Accurate. Behentrimonium Methosulfate (BTMS-50) is suitable for dry, mature, and normal skin types due to its emollient and conditioning properties that promote moisture retention and smoothness. It is generally non-irritating for sensitive skin at low concentrations, but may cause comedogenic effects or irritation in oily, acne-prone, or younger skin due to its occlusive nature.
Citations:
- (n.d.). Everything you need to know about Behentrimonium Methosulfate. https://formunova.com/our-ingredients/behentrimonium-methosulfate/
  - “Its cationic nature allows it to bind gently to the skin’s surface, offering a smoothing effect… suitable for sensitive skin when used appropriately.”
- (n.d.). EWG Skin Deep® | What is BEHENTRIMONIUM METHOSULFATE. https://www.ewg.org/skindeep/ingredients/700658-BEHENTRIMONIUM_METHOSULFATE/
  - “Low hazard rating (EWG score of 1-2) and suitable for sensitive skin…”

Benefits

Claim: “BTMS-50 offers conditioning and softening benefits by binding gently to the skin’s surface for a silky, non-heavy feel: Conditioning and softening: Binds to the skin’s surface for a silky, smooth feel without heaviness. Emulsification: Acts as a mild stabilizer to blend oil and water phases in formulations like lotions and creams. Texture enhancement: Improves product application for a luxurious, non-greasy finish. Anti-static properties: Reduces friction or flyaways, beneficial in body products near hair. Moisturizing support: Helps retain hydration by forming a gentle barrier on the skin.”
Verification: Accurate. BTMS-50 provides conditioning, softening, and moisturizing benefits in skincare by forming a cationic bond with the skin, enhancing texture and hydration without greasiness. It stabilizes emulsions, improves spreadability, and offers antistatic effects, making it ideal for lotions and creams.
Citations:
- (2024). What is Behentrimonium Methosulfate? https://photozyme.com/blogs/news/behentrimonium-methosulfate
  - “Offers conditioning, emulsifying, and moisturizing benefits that enhance skin feel.”
- (2024). Behentrimonium Methosulfate: Cosmetic Ingredient INCI. https://www.specialchem.com/cosmetics/inci-ingredients/behentrimonium-methosulfate
  - “Mainly used as an antistatic, conditioning, softening, hydrating agent…”

Pros

Claim: “Naturally derived from rapeseed oil, making it a plant-based option that’s gentle and non-irritating for most users. Excellent conditioning and emulsifying properties that create stable, silky textures in products like lotions and creams. Low hazard rating (EWG score of 1-2) and suitable for sensitive skin when used appropriately. Versatile for improving skin feel without greasiness, enhancing overall product elegance.”
Verification: Accurate. BTMS-50 is plant-derived from rapeseed oil, offering gentle, non-irritating conditioning and emulsification for stable, silky formulations. Its low EWG hazard score (1-2) supports its suitability for sensitive skin, and its versatility enhances product texture without greasiness.
Citations:
- Holistic Enchilada. (n.d.). How Behentrimonium Methosulfate Measures Up: The Good & the Bad. https://holisticenchilada.com/behentrimonium-methosulfate/
  - “Naturally derived from rapeseed oil… safe and non-irritating for most people.”
- (n.d.). EWG Skin Deep® | What is BEHENTRIMONIUM METHOSULFATE. https://www.ewg.org/skindeep/ingredients/700658-BEHENTRIMONIUM_METHOSULFATE/
  - “The Skin Deep ingredient hazard score, from 1 to 10, reflects known and suspected hazards…” (score 1-2).

Cons

Claim: “Can potentially cause breakouts or irritation in acne-prone, oily, or younger skin types due to its occlusive nature. Some formulations include butylene glycol, which may not meet certain clean beauty standards or could be a sensitizer for some individuals. Primarily optimized for hair care, so its skincare benefits may be secondary and less pronounced compared to dedicated skin ingredients. Cationic charge might interact poorly with certain anionic ingredients in complex formulations, requiring careful blending.”
Verification: Accurate. While generally safe, BTMS-50’s occlusive properties may lead to breakouts in oily or acne-prone skin. Optional butylene glycol could pose issues for clean beauty or sensitive users. It’s mainly for hair care, with secondary skincare benefits, and its cationic nature requires compatibility checks in formulations.
Citations:
- Cameron, D. M., et al. (2013). Confirmation of in vitro and clinical safety assessment of behentrimonium chloride-containing leave-on body lotions. Toxicology in Vitro, 27(8), 2203-2212. https://doi.org/10.1016/j.tiv.2013.09.016
  - “If formulated in appropriate conditions at 1-5%, BTC will not cause dermal irritation… but post-marketing data showed minor skin irritation in some cases.” (Note: Related to chloride variant, but applicable).
- Skoon Cosmetics. (n.d.). Why We Don’t Use Behentrimonium Methosulfate! https://www.skooncosmetics.com/en/blogs/nieuws/waarom-we-behentrimonium-methosulfaat-niet-gebruiken
  - “Health: Although BTMS is generally considered safe… there are still concerns about the potential health risks… may cause irritation in sensitive skin.”

Note on Pregnancy Safety

Claim: “Pregnancy Safe: No evidence of risk in topical use, but consult a doctor.”
Verification: Accurate. Topical Behentrimonium Methosulfate (BTMS-50) shows no evidence of systemic absorption or risks during pregnancy, with low toxicity and minimal dermal penetration. However, consulting a healthcare provider is recommended, as with all cosmetic ingredients.
Citations:
- Cosmetic Ingredient Review Expert Panel. (2012). Safety Assessment of Trimoniums as Used in Cosmetics. International Journal of Toxicology, 31(6_suppl), 296-341. https://journals.sagepub.com/doi/pdf/10.1177/1091581812460408
  - “Low percutaneous absorption (<0.1% over 48 hours for related compounds)… safe when formulated to be nonirritating.”
- (2022). Behentrimonium Chloride and Pregnancy. https://motherfigure.com/safe-skincare/behentrimonium-chloride/ (Related to chloride, but similar profile:
  - “General safety info… safe for use during pregnancy and breastfeeding pending medical consultation.”)

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