Why copper peptide levels fall over time

Your body makes GHK. It is present in plasma, and it does not stay at the same concentration for life.

The figure usually cited comes from Loren Pickart, who first identified the peptide: plasma GHK sits at roughly 200 nanograms per millilitre in the early twenties, and closer to 80 by the sixties. Whether the precise numbers hold across every population is a fair question. The direction is not seriously disputed — the level falls.

What that does and does not tell you

It is tempting to draw a straight line from that curve to the face in the mirror. We would rather not.

Plasma concentration is not skin concentration. A measurement in blood does not tell you what is available in the dermis, and a declining average across a population does not predict any individual. Anyone selling you a molecule on the strength of a single graph is asking you to accept a much larger claim than the graph supports.

What is reasonable to say is narrower. Copper peptide is one of a number of signals skin uses, its availability changes over time, and the qualities people notice changing on the surface — how well skin holds water, how quickly it settles after being pressed, how light sits on it — are qualities that depend on the same structures copper-dependent enzymes help maintain.

What changes on the surface

Three things tend to shift, and they shift at different speeds.

Water. Skin that holds water reads plump and reflects light evenly. Skin that holds less reads dry in patches and catches light unevenly, which is why dryness so often looks like texture.

This is the fastest thing to move in either direction. It is also the easiest to influence from the outside, which is why almost any decent serum shows something in the first week.

Surface smoothness. Slower. This is the quality you notice in daylight rather than bathroom light, and the one that determines whether makeup sits flat or settles into fine lines. It tends to read differently somewhere around the fourth week of consistent use.

Firmness. Slowest, and the one worth being most careful about. What people mean by firmness is largely how skin behaves structurally — how it holds its shape, how it recovers. That is not a surface property, and nothing applied topically changes it quickly.

This is the honest reason our guarantee runs sixty nights rather than thirty. Thirty days is long enough to judge comfort and hydration. It is not long enough to judge the thing most people actually bought the serum for.

The part we will not claim

We will not tell you that Aijaé restores your skin to an earlier state, or reverses a decline, or turns a curve around. We do not know that, and neither does anyone selling you the same molecule with more confident language.

What a nightly dose of the Aijaé Peptide Serum does is put the signal back on the surface, consistently, in a form that can get past the barrier. Whether that matters to you is a question your own face answers over about eight weeks.

Why the delivery question comes next

All of the above assumes the peptide reaches living skin. That assumption is doing an enormous amount of work, and for most copper peptide products on the market it is not a safe one.

GHK-Cu is water-loving and relatively bulky. The outermost layer of your skin is a lipid barrier built specifically to exclude molecules like it. A percentage printed on a carton describes what went into the mixing vessel, not what crossed the barrier.

That gap — between the number on the label and the dose that arrives — is the single biggest reason copper peptide products disappoint. It is also the most solvable, and it is what the next piece in this journal is about.