The advice not to layer copper peptides with vitamin C has circulated for years as received wisdom, usually with a vague explanation about copper oxidising things. A 2026 paper published for entirely unrelated reasons, building a chemical sensor, put a number on what GHK-Cu actually does catalytically. It is the most concrete thing anyone has published on this question, and it still does not settle it.
This article covers GHK-Cu as a cosmetic ingredient. It is not medical advice, and nothing here has been evaluated by the FDA.
Key Takeaways
- A 2026 study characterised GHK-Cu as a laccase mimic, an enzyme-like copper oxidase, with a Vmax of 1.735 x 10-4 mM/s and a Km of 0.061 mM against a phenolic substrate [1].
- The researchers were not studying skincare. They built a colorimetric sensor for epinephrine and 2-aminophenol, including a cotton-based version for seawater [1].
- This is the first hard evidence that the GHK-Cu complex is catalytically active rather than a passive delivery vehicle for copper.
- It does not demonstrate that GHK-Cu degrades vitamin C. Ascorbic acid was not tested, ascorbic acid is not a phenol, and the conditions were analytical buffers and seawater, not a serum.
- The separate pH conflict remains real: L-ascorbic acid needs a low-pH vehicle, and formulation environment is a known problem for topical GHK [2].
What a Laccase Mimic Is
Laccases are copper-containing enzymes that oxidise phenolic compounds using oxygen. They show up in fungi, plants and bacteria and are used industrially for breaking down phenols. They are expensive and unstable, so there is an active research field looking for small molecules and nanomaterials that mimic what they do.
The 2026 Biosensors paper reports that GHK-Cu is one of those mimics [1]. The group measured enzyme kinetics on it: a Vmax of 1.735 x 10-4 mM/s and a Km of 0.061 mM, which they describe as good substrate affinity and efficient catalysis. They then used it to build colorimetric assays for epinephrine and 2-aminophenol, with detection limits in the low micromolar range, and a cotton-based sensor for detecting 2-aminophenol in seawater with a smartphone readout.
Nothing about that paper is aimed at cosmetics. That is part of why it is useful. It is a measurement of a chemical property with no product to sell.
Why This Is Relevant to Your Routine
The interesting shift is conceptual. GHK-Cu is usually discussed as a signalling molecule: it binds copper, delivers it, modulates gene expression [3]. This paper describes it doing chemistry, catalysing an oxidation reaction on a substrate.
A catalyst is not consumed by the reaction it drives. That is what makes catalytic activity worth taking seriously in a formulation context in a way that a stoichiometric reaction would not be. A small amount of an active complex sitting next to an oxidisable ingredient is a different situation from two inert ingredients coexisting.
That is the honest strength of this finding. Now the limits.
What This Study Does Not Show
It does not show that GHK-Cu degrades vitamin C. Three things stand in the way of that jump.
Ascorbic acid was not tested. The substrates were epinephrine and 2-aminophenol. Neither is vitamin C.
Vitamin C is not a phenol. L-ascorbic acid is an enediol lactone. Copper-catalysed ascorbate oxidation is separately well documented in chemistry, which is why formulators chelate trace metals out of vitamin C products, but the laccase-like activity measured here is characterised against phenolic substrates and cannot simply be extended.
The conditions were not a serum. Ultrapure water and seawater at analytical concentrations do not tell you what happens in an emulsion or a gel with chelators, antioxidants and a specific pH.
So the accurate position is that a mechanism which would make the folk advice correct has now been measured, and the specific interaction still has not been tested by anyone.
The pH Problem Is Separate and Also Real
Layering advice for these two ingredients often conflates two different objections.
L-ascorbic acid is formulated at low pH, commonly around 3.5 or below, because it needs that to remain stable and to penetrate. Copper-peptide products are not formulated there, and the vehicle a peptide complex sits in is one of the recurring practical obstacles in the topical GHK literature [2].
Applying a strongly acidic product on top of a copper peptide is a formulation environment issue, distinct from any catalytic reaction between the two molecules. Both objections point the same direction, which is why the practical advice is stable even though the evidence is thin.
What to Actually Do
Separate them. Vitamin C in the morning, GHK-Cu at night, is the simplest version, and alternate days works equally well if your skin prefers that.
The reasoning is asymmetric in a useful way. If the interaction turns out to be irrelevant, separating them costs you nothing except a small amount of routine planning. If it is real, you have protected two of the more expensive things in your cabinet. There is no scenario where layering them delivers a benefit that separating them does not.
Vitamin C derivatives such as ascorbyl glucoside or sodium ascorbyl phosphate are formulated at higher pH and are more stable, which removes the pH objection. Whether they remove the oxidation objection is untested, so the same separation logic is worth keeping.
What nobody should tell you is that this is settled. The most specific published fact is that the copper peptide complex is catalytically active as an oxidase, measured for a sensor application, on substrates that are not vitamin C.
Frequently Asked Questions
Can you use GHK-Cu and vitamin C together?
No published study has tested a copper peptide serum layered with a vitamin C serum on skin, so nobody can answer this from data. The cautious approach, and the one most formulators take, is to separate them into different routines.
Does GHK-Cu destroy vitamin C?
That specific claim has not been tested. What has been shown is that GHK-Cu itself has laccase-like oxidase activity with measurable kinetics [1], meaning the complex can catalyse oxidation reactions rather than being chemically inert next to an antioxidant.
Is the problem pH or oxidation?
Potentially both, and they are separate issues. L-ascorbic acid needs a low pH to be stable and to penetrate, which is a poor environment for the copper-peptide complex [2], and the oxidase activity is a distinct concern about what the copper centre does chemically [1].
What is the practical answer?
Use them at different times, vitamin C in the morning and GHK-Cu at night or on alternate days. That costs you nothing if the interaction is irrelevant and protects both products if it is not.
References
- Chen JS, Zhu H, Chai TQ, Yang FQ. The Laccase-like Property of GHK-Cu and Its Applications in Colorimetric Sensing of Phenolic Compounds. Biosensors (2026). PMID 42041438
- Mortazavi SM, Mohammadi Vadoud SA, Moghimi HR. Topically Applied GHK as an Anti-Wrinkle Peptide: Advantages, Problems and Prospective. BioImpacts (2025). PMID 39963574
- Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. International Journal of Molecular Sciences (2018). PMID 29986520 (authors affiliated with Skin Biology, a company that sells copper-peptide products)
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical or dermatological advice. As an Amazon Associate we earn from qualifying purchases.
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
