After recently adding a vitamin C serum into my routine (Paula's Choice C15 booster), I am hoping that I have found a more reasonably priced alternative (NuFountain C20+Ferulic) to continue using long-term ($48 for 0.67 oz vs $21.99 for 1 oz). I like using the PC booster exactly as indicated: adding it into my current lotions to "boost" their performance. This is super convenient because it doesn't alter my existing routine, AND I can mix it into my body lotion and get this serum's benefits all over without going bankrupt. However... while this is awesome in theory, I am super confused about how the PC booster actually works when mixed with other products. Since ascorbic acid requires a Ph below 3.5 to remain stable, how can the PC booster possibly maintain this when mixed with any variety of unknown products? I emailed PC customer service to specifically ask this question and the answer they gave me was very unsatisfying. They said the serum was formulated with this in mind and it has penetration enhancers to ensure that the ascorbic acid is viable when mixing. Here is the full ingredient list:
Water, Ascorbic Acid (vitamin C/antioxidant), Ethoxydiglycol (slip agent/penetration enhancer), PPG-26 Buteth-26 (emulsifier), PEG-40 Hydrogenated Castor Oil (thickener), Tocopherol (vitamin E/antioxidant), Ferulic Acid (antioxidant), Sodium Hyaluronate (skin-repairing ingredient), Acetyl Octapeptide-3 (cell-communicating ingredient), Glycerin (skin-repairing ingredient), Panthenol (skin conditioning agent), Sodium Metabisulfite (stabilizer/antioxidant), Triethanolamine (pH adjuster), Phenoxyethanol (preservative)
Now, as for NuFountain, I emailed their customer service and asked about mixing their product into a cream immediately before applying and got a very different answer. Their logic is on the same line as mine with the PC booster: It needs a special Ph to be stable, so mixing it will likely affect the Ph and render the ascorbic acid useless. They not only said that their serum should not be mixed with others before applying, but also that their serum should be applied first to allow full absorption of the ascorbic acid without any chance of altering its efficacy. Here is the full ingredient list of that serum:
Purified Water, 20% L-Ascorbic Acid, Ethoxydiglycol, DL- Panthenol, Glycerin, Magnesium Sulfate, Ferulic Acid, Sodium Hyaluronate, Sodium PCA, Phenoxyethanol, Caprylyl Glycol, Sorbic Acid
There are a couple of additional ingredients at the end of the PC booster ingredient list, but the only penetration enhancer (the star player of the booster serum according to the PC email) is present in both serums. So what is going on? Are these two serums really redically different in terms of stability, or is someone just wrong here?