What is GHK-Cu? The copper peptide, explained

Most actives in skincare work by force. Acids dissolve the bonds between surface cells. Retinoids push turnover faster than skin would choose. They work, and the irritation is part of how you know they are working.

Copper tripeptide-1 does not belong to that group. It is a signal, not a stressor — and understanding the difference is most of what you need to know about it.

Three amino acids and a copper ion

GHK is a tripeptide: glycine, histidine and lysine, joined in that order. On its own it is unremarkable. What makes it interesting is that it binds copper with unusually high affinity, forming the complex written as GHK-Cu.

That complex is what gives a well-made copper peptide serum its blue colour. The colour is not a dye. It is the copper.

GHK was identified in 1973 by Loren Pickart, working with human plasma. He was studying why plasma from younger donors behaved differently from older plasma in tissue culture, and traced part of the difference to a small peptide fraction. It has since been found in saliva and urine as well as plasma.

Why copper, specifically

Copper is not incidental to the molecule. It is a required cofactor for a family of enzymes your skin uses constantly — among them lysyl oxidase, which cross-links the structural proteins in the dermis, and superoxide dismutase, one of the body's own antioxidant enzymes.

Free copper on skin is a poor idea; it is reactive and can drive oxidation rather than limit it. Bound into a peptide complex, it is stable and can be carried where it is useful. That is the practical argument for a peptide-copper complex over a copper salt.

What a signal molecule actually does

The useful mental model is a message rather than a tool. GHK-Cu does not abrade, dissolve or accelerate. It arrives, and the skin responds — or does not.

This is why copper peptide behaves so differently in a routine. There is no purging phase, because nothing is being forced to the surface faster than usual. There is no photosensitivity, so it does not dictate when you can use it. There is no cycling on and off, because there is no accumulating irritation to recover from.

It is also why results read slowly. A signal repeated nightly for two months is a different proposition from an acid that visibly resurfaces in a week. Hydration reads first. Surface smoothness follows. The changes people describe as firmness are the slowest of the three.

What we will not claim

The biochemistry above is well established. The distance between that biochemistry and what a cosmetic serum does on your face is not, and we would rather name the gap than paper over it.

We will not tell you that Aijaé stimulates collagen synthesis. We will not describe it as anti-ageing. We will not present laboratory findings on isolated cells as though they were results on skin.

What we will say is narrower and, we think, more useful. Copper tripeptide-1 is one of the most studied signal peptides in skin science. It is exceptionally well tolerated. And in a formula built to carry it past the surface, people consistently report skin that holds water better, reads smoother in daylight, and looks firmer over months rather than weeks.

The part most brands leave out

A peptide that never reaches living skin is a peptide you paid for and did not receive. GHK-Cu is water-loving and comparatively large; your barrier is built to keep exactly that out. Most of the percentage printed on a bottle sits on the surface and washes off.

That is a formulation problem rather than an ingredient problem, and it is the subject of a separate piece in this journal.

The other half of the question is simpler: is the percentage on the label the percentage in the bottle? For most products, nobody has measured. For the Aijaé Peptide Serum, batch AJ-0426 was assayed by HPLC at 2.03%, and the certificate travels with the batch number on your bottle.