GHK-Cu vs AHK-Cu

Two copper tripeptides sold side by side — does either have evidence for skin or hair?

No head-to-head trial — cross-trial comparison
In one paragraphGHK-Cu has small, short, mostly industry-run human trials of creams for skin appearance and one mixed wound-healing study; that is thin, but it is human evidence. AHK-Cu has none: its entire file is one 2007 study in which plucked hair follicles lengthened in a dish. Neither has ever been injected in a trial, and both are sold for injection. If the question is 'which has evidence', the answer is GHK-Cu, topically, modestly.

Side by side

C GHK-CuD AHK-Cu
LYO gradeCD
SequenceGly-His-Lys · copperAla-His-Lys · copper
Human trialsSmall topical trials (12-week facial studies; a 1990s diabetic-ulcer gel)None
Best evidenceImproved skin laxity, clarity and fine lines vs vehicle in small industry studiesFollicle elongation ex vivo, 2007 (Pyo et al.)
Hair growth in peopleNo trialNo trial
Injected useNo human studyNo human study
Regulatory statusCosmetic ingredientCosmetic ingredient
Sport (WADA)Not listed by nameNot listed by name
Verdict

GHK-Cu for topical skin use, on modest evidence. AHK-Cu for nothing yet — its hair claim has not been tested on a person. Injected use of either has no evidence at all.

What GHK-Cu's evidence actually is

GHK-Cu occurs naturally in plasma and falls with age, which is the origin of the anti-ageing story. The human trials are of creams: twelve-week facial studies from the late 1990s and early 2000s that measured skin laxity, clarity and fine lines against vehicle or a comparator, and a gel tested on diabetic foot ulcers with mixed results. They are small and mostly funded by the makers. They are also the only controlled human data for any copper peptide.

What AHK-Cu's evidence actually is

One study. In 2007 human hair follicles were plucked, kept alive in culture for a week, and exposed to AHK-Cu at nanomolar concentrations; they grew longer, and dermal papilla cells divided more. The anti-apoptotic effect the study set out to show was not statistically significant. No one has since applied AHK-Cu to a scalp under controlled conditions. Every hair-growth claim online traces to that dish.

The injected versions

Both peptides are now sold as injectables, sometimes together. There is no human study of injected GHK-Cu or AHK-Cu — no dose, no distribution, no safety. Copper is essential and also toxic in excess; injecting a copper complex on the strength of cream trials and a follicle culture is an extrapolation with nothing underneath it.

Questions people actually ask

Is AHK-Cu better than GHK-Cu for hair?
Unknown. Neither has a human hair-growth trial. AHK-Cu's follicle-culture result is the only data point, and it is not a clinical one.
Can GHK-Cu and AHK-Cu be combined?
They are sold that way. No study has tested the combination in people, topically or injected.
Which is safer?
As cosmetic ingredients applied to skin, neither has a reported safety signal. Injected, neither has any safety data.

References

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    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, 2018Review by the peptide's discoverer; summarises the topical trials.