Peptides in cosmetics

Peptides have become almost obligatory on cosmetic product labels. The problem is that very different molecules, with different roles, hide behind the same word. This text explains how they are classified, how their INCI names are read and what can reasonably be expected from them.

If you need the basics, start with the text What are peptides.

How a peptide’s INCI name is read

A peptide name usually has three parts.

The prefix is the molecule attached to the peptide chain. The most common ones are:

• Acetyl, an acetyl group, improves stability
• Palmitoyl, a fatty acid, makes it easier to pass through the skin’s lipid layer
• Biotinoyl, attached biotin
• Myristoyl, another fatty acid, a role similar to palmitoyl

The root indicates the length of the chain: Dipeptide, Tripeptide, Tetrapeptide, Pentapeptide, Hexapeptide, Oligopeptide.

The number at the end identifies the specific molecule within that group. It is not strength, not concentration, not a generation. Tetrapeptide-3 and Tetrapeptide-30 are two different molecules, not two versions of the same one.

Four groups by role

Signal peptides

The largest group in skincare products. The idea is that the fragment resembles part of a natural protein and can take part in the communication that happens in the skin anyway.

Many peptides found in face and scalp products belong here.

Carrier peptides

Their role is to bind a trace element and keep it in a stable, usable form. The best known representative is the copper tripeptide, described in the text GHK-Cu, copper peptide.

Enzyme inhibitors

They slow down the enzymes that break down certain structures in the skin. In cosmetics they are used in products for firmness and elasticity.

Neurotransmitter peptides

They affect signal transmission to muscle fibres. They are known from products aimed at facial expressions. In scalp products they have no role.

Three peptides found in scalp products

Copper Tripeptide-1, the copper tripeptide, GHK-Cu. The most studied peptide in this group.

Biotinoyl Tripeptide-1, a tripeptide with attached biotin. Used in hair and scalp care products.

Acetyl Tetrapeptide-3, a synthetic tetrapeptide, common in formulations intended for the scalp.

All three are in the composition of the SORA peptide hair set.

Why peptides are always near the bottom of the INCI list

The INCI list is given in descending order of proportion, but only down to the one per cent mark. Below that mark the order is not mandatory.

In cosmetics peptides are used in very low concentrations and are almost always in that lower part of the list. This is expected and says nothing bad about the product. What would be suspicious is a peptide at the top of the list, because that would mean an unusually high proportion.

Stability and packaging

Peptides are sensitive to storage conditions. Heat, light, air and pH value affect their stability in a formulation.

For that reason they are often packaged in opaque bottles, in single dose ampoules or as a concentrate that is prepared immediately before use. The type of packaging is a useful piece of information: it shows that the manufacturer took this into account.

What can reasonably be expected

A peptide is an ingredient with a reason to be in a formulation. It is not magic and it is not a medicine.

Published research usually concerns the ingredient under controlled conditions, with a specific concentration and carrier. A finished product is something else: its effect depends on the formulation, the concentration, how it is applied and how regularly.

So it is reasonable to see peptides as a sensible part of a routine rather than as a solution. When a condition requires a doctor, cosmetics have no role, as described in the text Alopecia.

In short

A peptide is recognised by its INCI name made of a prefix, a root and a number. The number identifies the molecule, not the strength. Peptides are divided into four groups by role and are always near the bottom of the ingredient list, which is normal. Packaging that protects the contents from light and air is a good sign.

Related: The SORA range of peptide complexes