
There is one question I wanted to ask for some time... It's quite a simple one.. I am not sure if there is a simple answer to it of course. I alway's say: "one nutcase can ask more questions than ten nutcases can answer"

Let's suppose one uses a day cream with 10% actives in it plus a toner with 8% actives and maybe even a serum on top. And it's al water soluable (does that matter?). Is that just not advisable? I mean that's 18% actives put right on the skin. Or is it sometimes advisable, but only with some ingredients and not with others? How does it add up? Are there any guidlines for that?
Thanks in advance