Preservative: Cosmocil CQ

Cosmocil CQ is a really novel preservative, relying upon polyhexamethylene biguanide (PHMB) as the preservative, which is neither a formaldehyde releaser nor a paraben based product. The INCI is polyaminopropyl biguanide. It's both a bacteriostatic and bactericidal preservative that should be combined with a fungicide like one of the parabens, potassium sorbate, or sodium benzoate (one of the organic acids).

In my research, I have found so many conflicting bits of information about this preservative, even from the company (Arch Chemicals) in their data sheets, so I've done my best to distill it all down to something easier to understand!   

It's cationic and the manufacturer notes it is incompatible with what they call strongly anionic systems, so I'd be careful using it with shampoo, body wash, and other foamy surfactant mixes. It is effective for pH 4 to 10, so you can use it with pretty much any product we make, with the ideal being below 6. It's soluble in water, ethanol, glycerin, and propylene glycol but insoluble in vegetable and mineral oils and esters, so you'll want to use in products that contain water. You can use it in your creations in the water phase while you heat it or add it just before emulsification. (One data sheet says it's heat stable to 140˚C, but when do we ever reach those temperatures? So I'm going with the stable to 80˚C suggestion.) The most frequent suggestion is that we should add it to the water phase before heating.

Summary of Cosmocil CQ
INCI: Polyaminopropyl biguanide
Usage: From 0.05% to 1.5%. Approved at up to 1.5% in the EU and 0.5% in Japan.
Not suitable for anhydrous products. Add in the heated water phase of your products pre- or post-emulsification.
Suitable for products with pH 4 to 10.