Preservatives: Mikrokill COS

madpiano asks in this post: I do have a question though, as we are in Europe, we have slightly different preservatives available. I mainly use one called Microkill, it's INCI is: Phenoxyethanol (and) Caprylyl Glycol (and) Chlorphenesin. Is there anything I need to watch out for? I know there is a similar US one, but that contians an acid as the 3rd ingredient, I am not sure how that compares to Chlorphenesin. The MSDS says stable at PH 3-8, which seems to cover all the things I make that need preservative.

Mikrokill COS is an interesting preservative from Arch Chemicals is a lot like Optiphen in that it contains phenoxyethanol and capryl glycol, but they've added chlorphenesin, an anti-fungal ingredient, which makes it a broad spectrum preservative.

We know phenoxyethanol is effective against bacteria and yeast, and we know that capryl glycol is an effective bacteriostatic ingredient, but what's up with chlorphenesin? (Click for the data sheet on this ingredient.)

Chlorphenesin is a muscle relaxant with anti-fungal and some anti-bacterial properties. Its irritation potential for our skin is on par with phenoxyethanol, which is in the middle of the irritation scale, but its subjective irritation is higher, meaning that although there wasn't much physical irritation, people reported feeling it irritated their skin more. Figure that one out!

Mikrokill COS is good for products with a pH of 3 to 8, and it can be used at 0.75% to 1.5% in the cool down phase, around 60˚C. It's not good for all oil or all water products, but it can be solubilized with a 1:1 ratio of Mikrokill COS to polysorbate 20 mixture for something like a toner or a shampoo. SLS will also solubilize this preservative.

Summary of Mikrokill COS
INCI:  Phenoxyethanol (and) Caprylyl Glycol (and) Chlorphenesin
Usage: 0.75% to 1.5% in products that contain oil and water. If you want to use it in all water products, solubilize it with 1:1 polysorbate 20.
Add it to the cool down phase when your product is lower than 60˚C.
Suggested pH level is 3 to 8.