Interactions Between Topical Active Ingredients

[SomeoneHasToSayIt]

I have a question for some of the topical mixers on here. How do you determine if two ingredients can be mixed without interacting in a negative way? Are there some basic chemistry principles that can be applied? Do you look for research?

I'm curious about using CB, topical finasteride, zinc, and maybe cetirizine, but I have no idea if they can realistically be combined. Thoughts? Thanks.

 

[John Difool]

Not so much about their interaction (also so people will argue about that) vs the fact that they can be dissolved in the vehicle(s) you want to use. Start by understanding the solubility factor then the quantity of solvent you need to get them dissolved. When you combine you will need more solvent to dissolve. Then figure out the stability in solvent and/or water because that will tell you how much your batch size will be. People do weekly or monthly batches based on how stable components are. It's not terribly complicated but you really want to make sure that what you put in the bottle will end up inside your scalp not just on top of it.