Cetrimonium Chloride

What it is

Cetrimonium chloride is a quaternary ammonium compound and thus a close relative of behentrimonium chloride. The difference lies in the length of the fatty chain: here it goes back to cetyl alcohol and is markedly shorter. The principle of action is the same — the permanent positive charge deposits on the negatively charged hair surface, preferentially on damaged areas.

Because the substance has a shorter chain and is therefore more water-soluble, it is used more widely: in conditioners, but also in reshaping and straightening products, where it additionally acts as an emulsifier. As with all substances in this group the effect rests on remaining on the fibre; nothing is built into it.

Why

• The principle of action is a charge, not a nutrient. What is perceived as conditioning is a surface effect: less friction, less static, easier combing. A real benefit, but not a repair.
• The shorter fatty chain is the difference from its relative behentrimonium chloride. It makes the substance more water-soluble and more widely usable. On irritant potential, general experience holds that shorter-chain members of this group tend to be more irritating than longer-chain ones; that is an assessment of the substance class and is not backed by data here.
• Raw material and product have to be kept apart. The concentrated raw material is irritating to eyes and skin; in the finished product the substance is heavily diluted and, in conditioners, rinsed out as well. Both statements are correct and describe different situations.
• Why the classification reads “low risk”: because of the predominantly rinse-off use, the short contact time and the molecular size, which makes appreciable uptake through intact skin unlikely. For products that stay on the scalp the question would have to be asked afresh.
• Not transferable: the debate about quaternary ammonium compounds as disinfectants, for instance benzalkonium chloride, concerns other molecules at other concentrations and in other uses. A shared substance class does not justify a shared assessment.

When the assessment differs

• Irritated, broken or inflamed scalp skin: the classification applies to intact skin.
• Products that stay on hair and scalp: longer contact time; the classification is less robust here than for rinse-off products.
• Eye contact: cationic surfactants irritate the eyes; practically relevant during application and rinsing.
• Fine hair and frequent application: a deposit is more likely to be felt as weighing the hair down. That concerns the result, not safety.
• Occupational contact: daily use on many heads compared with occasional use on one.

Open questions

• Concentration in the actual product: not available. It matters a great deal here, because the substance is used both as a conditioning agent and as an emulsifier, and the amounts differ accordingly.
• Comparison of irritant potential between short-chain and long-chain members: not backed by data here. The statement above is an assessment of the substance class.
• Regulatory status: not checked; statements on use and maximum levels are not quoted second-hand.

Related substances

Applies to: Cationic conditioning agents

• Behenamidopropyl Dimethylamine — Conditioner, antistatic agent
• Behentrimonium Chloride — Cationic conditioner, detangler
• Polyquaternium-10 — Detangling, conditioning
• Polyquaternium-7 — Cationic conditioning polymer

Further substances from the same group for which a long-form assessment already exists.