We spent a great deal of time trying to define the idea of "cosmeceutical" and "active" in this post, so let's get to the next parts of the questions posed in my October Q&A on Patreon.

Michelle asked: I am wondering what exactly is considered an 'active' ingredient, and if there is a maximum percentage recommended for total active ingredients in a formulation.

In the same post, Belinda said: I will second Michelle?s comment. I, too, have been wondering how many cosmeceuticals is too many. Right now I?m experimenting with the ones I have one at a time, but when I?m sure I?m not reacting to any of them individually, I?d like to use combinations of them in an anti-aging facial lotion. Are there any guidelines for formulating with multiple cosmeceuticals"
In the same post, Mimi added: I have the same question as Michelle and Belinda.  Is there a limit to how many cosmeceuticals you can add to a face cream"  I put about 6-7 anti aging products that I bought from Lotioncrafter into 1 face cream, but I'm not sure doing this will cause one product to react with another and nullify the effectiveness. 

As there's no real definition of what active might be, I'll go with the Australasian College of Dermatologists defintion:
Cosmeceuticals are products that have both cosmetic and therapeutic (medical or drug-like) effects, and are intended to have a beneficial effect on skin health and beauty. Like cosmetics,...