I've been using it for several years now and at this point I know 4 things about it.
First, it's expensive.
Second, I have no idea what it really is supposed to be doing for me. I've actually gone to the Skinceuticals website to try to understand what this actually does - I still don't know.
Third, since I didn't really know what it was doing, I stopped using it for about 3 weeks this past winter, to disastrous results.
Fourth, I cannot live without it.
Can anyone explain to me why the blocking of free radicals is so important to one's skin?