Are their rules for combining different ionic ingredients
I am formulating a shampoo bar using Sodium Cocoyl Isethionate as my main surfactant, which is compatible with anionic, non-ionic and amphoteric surfactants. Is it advisable to include BTMS-25 which is cationic? Is there rules about combining ingredients of this nature? My goal would also be to achieve a pH of 5.5-7, will preservatives be necessary if the formulation is anhydrous or would the surfactants be sufficient enough in retarding the growth of pathogens on the areas exposed to water? I have seen a few research study’s and anecdotal evidence that leads me to believe it may be fine. Any advice is greatly appreciated, thank you!