# Can you use copper peptides with vitamin C? You can, with a minute between them, or you can split them across morning and night and remove the question entirely. The concern is real chemistry: copper ions catalyze the oxidation of ascorbic acid in solution, documented since 1969. No study has tested whether that matters on skin at cosmetic levels. We sell both, so here is the honest version. Canonical: https://existentialcosmetics.com/guides/copper-peptides-and-vitamin-c ## What is the conflict between copper peptides and vitamin C? The chemistry is not in dispute. Copper ions accelerate the oxidation of ascorbic acid in solution, which Hanaki showed in 1969 and nobody has needed to show again. Oxidized ascorbic acid is spent ascorbic acid. So if you dissolve L-ascorbic acid and free copper in the same beaker, the vitamin C degrades faster than it would alone. What is in dispute is whether any of that happens on skin. Copper tripeptide-1, GHK-Cu, holds its copper with high affinity; it is a complex, not a sprinkle of free ions. L-ascorbic acid serums sit at a pH near 3, which is not where a copper peptide complex is at its most stable either. Both of those are formulation facts about a bottle. Nobody has run the skin study at cosmetic concentrations, so the evidence level here is chemical plausibility, not clinical proof. We would rather say that plainly than pick a side and pretend. ## What do copper peptides actually do? GHK-Cu is a three amino acid peptide that binds copper, occurs naturally in human plasma, and declines steeply with age. In cell and tissue models it stimulates collagen, elastin and glycosaminoglycan synthesis and supports dermal fibroblast function. Gene profiling work reports it shifting a large number of human genes toward a repair-associated pattern; the 2018 review by Pickart and Margolina in the International Journal of Molecular Sciences collects that data across skin, lung, bone, liver and stomach models. Nearly all of it is preclinical. That is why copper tripeptide-1 sits in our interesting tier, and why the label says so. It is also what makes the serum blue. Copper peptides tint a formula, and we decided the honest color was better than hiding it. ## How should you layer vitamin C and copper peptides? Two options, both fine. The first is the order we use in the morning: vitamin C onto clean, dry skin, a full minute for it to absorb, then the peptide serum. Once the vitamin C has gone in, the surface is no longer a pH 3 solution and the two are not sitting in the same wet layer. The second option costs nothing and ends the debate: vitamin C in the morning, copper peptides at night. Put the peptide serum on before your retinal and let it absorb. Either way the question stays academic, which is where it belongs until somebody runs the study. - Same routine: Bright Side, one minute, Mixed Signals. - Split routine: Bright Side in the morning, Mixed Signals at night before Coming of Age. - Either way, never in the same wet layer. ## Do acids and retinal break down copper peptides? Strong direct acids are the thing to keep out of the same layer. Peptides are more stable near neutral pH, and a high-percentage exfoliating acid on top of a peptide serum is asking the peptide to sit somewhere it does not want to be. Retinal is not an acid. Peptides and retinal on the same night, with a minute between them, is fine, and it is how the night version of our routine works. ## What we made with it Bright Side is the vitamin C: 15% L-ascorbic acid with vitamin E and ferulic acid. Mixed Signals is the copper peptide serum: copper tripeptide-1 and palmitoyl pentapeptide-4 for the interesting work, 5% niacinamide for the well-documented work. In the morning routine they go on in that order with a minute between. If you would rather split them, Mixed Signals moves to the night, before Coming of Age. ## Related questions **Do copper peptides actually work?** In cell and tissue models, convincingly: collagen, elastin and glycosaminoglycan synthesis go up and gene expression shifts toward repair. On faces the trials are smaller and newer. We wear it because the mechanism is real and the research keeps deepening, and we label it interesting so you know exactly what you are getting. **Why is the serum blue?** Copper. Copper tripeptide-1 carries a copper ion and copper complexes are blue. It is the color of the ingredient, not a dye, and we left it alone rather than covering it up. **Can I use copper peptides with retinal?** Yes. Retinal is not an acid and there is no documented interaction. Apply the peptide serum first, wait a minute, then the retinal, then your barrier cream. That is the night version of our routine for anyone who wants Mixed Signals away from the vitamin C. ## Sources 1. Hanaki A. Copper-catalyzed oxidation of ascorbic acid. Chem Pharm Bull 1969. (PMID 5347591) https://pubmed.ncbi.nlm.nih.gov/5347591/ 2. Pickart L, Margolina A. Regenerative and protective actions of the GHK-Cu peptide in the light of the new gene data. Int J Mol Sci 2018;19:1987. (PMID 29986520) https://pubmed.ncbi.nlm.nih.gov/29986520/ 3. Murray JC, et al. A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation. J Am Acad Dermatol 2008;59:418-425. (PMID 18603326) https://pubmed.ncbi.nlm.nih.gov/18603326/