AHK-Cu is a copper peptide. Acetyl Tetrapeptide-3 is a topical skincare peptide.
| Comparison | AHK-Cu AHK copper · Ala-His-Lys copper | Acetyl Tetrapeptide-3 Capixyl · tetrapeptide-3 |
|---|---|---|
| How it works | How it works Copper peptides work as a delivery system. The peptide part holds the copper and carries it where a plain copper salt could not go. | How it works This peptide is sold to strengthen how firmly a hair sits in the scalp, rather than to grow new hair directly. |
| What it is | GHK-Cu's less-studied cousin, sold mainly for hair. | A hair peptide sold for thinning, with evidence that mostly belongs to a combination product. |
| Status | Sold over the counterCosmetic ingredient | Sold over the counterCosmetic ingredient |
| Typical dose | — | — |
| How often | Daily | Daily |
| Stays active | Not measured, and not the right question | Not measured, and not the right question |
| Dose comes from | No established range | No established range |
| Cycled? | Applied daily, with no established course Community practice | Not cycled Community practice |
| What it does | ||
| Drug class | Copper peptide | Cosmetic peptide |
| Used for | Applied to the scalp or skin, mostly marketed for hair thickness. | A scalp peptide used for thinning hair and weak anchoring, usually as part of a branded blend rather than on its own. |
| Receptors hit | — | — |
| Numbers | ||
| Full dose line | Topical serum, per product | Serum or scalp treatment, 0.1 to 5% |
| Why that cycle | Treated like a skincare ingredient rather than a course of treatment. No study has tested a duration. | Used daily as part of a routine. The effect depends on continued use and fades when you stop, so there is nothing to cycle off. |
| Weight / effect | Not measured in a trial | Not measured in a trial |
| Chain length | 3 residues | 4 residues |
| Common vial | 50 mg | — |
| Before you start | ||
| Route | On the skin (topical) | On the skin (topical) |
| Do not use if | Known copper allergy Wilson's disease, a condition where copper builds up in the body Broken or badly irritated skin | Broken or actively inflamed scalp skin A known allergy to any component of the finished product |
What separates them
Proof behind the dose. Every dose here comes from community practice. Not one is backed by a published human study, which is worth knowing before you read the numbers as if they were equivalent.
What doesn't differ: They are both taken the same way (on the skin), aimed at the same thing (hair growth) and on the same schedule (daily). Neither has a measured effect size from a published trial, so there is no number to rank them on.
What people actually report
AHK-Cu
- Generally well tolerated on the skin.
- Much less studied than GHK-Cu, which is the peptide most of its claims borrow from.
- A spreading rash or burning where it was applied
- Signs of an allergic reaction
Acetyl Tetrapeptide-3
- Very well tolerated in cosmetic use.
- Occasional scalp irritation, usually from other ingredients in the formula.
- A spreading rash or significant swelling where applied
Side effects are what users and trials report most often, not a complete list. Anything sudden, spreading, or breathing-related is an emergency regardless of which compound caused it.
People also compare
This comparison does not cover cost, long-term safety, or how you personally will respond. Effect figures come from separate trials in different populations and are not always directly comparable to each other. Nothing here is medical advice or a recommendation to use any of these. Talk to a clinician about your own situation.