What is it? Cetrimonium chloride

Other names it goes by? Cetyl trimethyl ammonium chloride, hexadecanaminium, trimethyl-chloride.

What's it used in? Hair colour products and bleaches, styling products, shampoos and conditioners.

What does it do? It's used as a preservative for its anti-microbial effects. Also used as an emulsifier and antistatic agent.

Any controversy? Tests show toxicology concerns for the immune system which include skin reactions such as itching, burning and blistering when applying products with this compound.