Peptides in Skincare: What Do They Actually Do
VOLUME THREE — SKIN INGREDIENTS
Article 6 - Peptides
Peptides in Skincare: What They Actually Do
“Peptides aren’t one ingredient with one job. They’re a family of signalling molecules — and what they do depends on the peptide itself.”
Peptides have become one of the most frequently promoted ingredients in healthy-ageing skincare.
They’re associated with:
- collagen
- firmness
- elasticity
- repair
- skin resilience
- reduced appearance of fine lines
And unlike some skincare trends, there is genuine science behind certain peptides.
But the category is also heavily marketed.
Not all peptides behave the same way. Not every peptide penetrates skin equally well.
And not every claim you see on a serum bottle is supported by strong human clinical evidence.
Reviews of topical peptides consistently note that while some peptide classes are promising, the strength of evidence varies considerably between individual ingredients.
So the useful question isn’t:
“Does this product contain peptides?”
It’s:
"Which peptides are in it, what are they designed to do, and is the formulation capable of delivering them effectively?”
What Are Peptides?
Peptides are short chains of amino acids.
Amino acids are the building blocks used to create proteins such as:
- collagen
- elastin
- keratin
- enzymes
- structural proteins
But peptides aren’t simply tiny pieces of collagen that get applied to your face and turn into new collagen.
Their role can be much more sophisticated.
Certain peptides can act as biological signals, interacting with cells or biochemical pathways involved in processes such as extracellular-matrix production, tissue repair and skin function.
That’s why different peptides are grouped according to what they’re designed to do.
The Main Types of Peptides Used in Skincare
1. Signal Peptides
Signal peptides are probably the category most people associate with healthy ageing.
They are designed to mimic fragments or signals involved in extracellular-matrix turnover.
The theory is that these signals can encourage fibroblasts to increase production of structural components such as:
* collagen
* elastin
* fibronectin
* other extracellular-matrix proteins
Signal peptides are among the most commonly investigated cosmetic peptides.
One of the best-known examples is: Palmitoyl Pentapeptide-4
You may also see this referred to historically as Pal-KTTKS.
Clinical research has reported improvements in wrinkles with topical palmitoyl pentapeptide formulations.
But that doesn’t mean every peptide serum containing a trace amount of a peptide will deliver the same outcome.
Concentration, vehicle, stability and delivery still matter.
2. Carrier Peptides
Carrier peptides are designed to help deliver trace elements important for skin function.
The most famous example is:
Copper Tripeptide-1 / GHK-Cu
GHK is a naturally occurring tripeptide.
When complexed with copper, it forms GHK-Cu.
Copper is involved in many biological processes related to connective tissue and repair, and GHK-Cu has been investigated for roles in wound healing, remodelling and skin regeneration.
Reviews report promising effects on collagen, elastin, glycosaminoglycan synthesis and tissue repair, although the quality of human clinical evidence is not equally strong for every cosmetic claim.
Copper peptides are interesting enough that I think they deserve their own later article in this Volume Three Series rather than being buried inside this one. So we will expand on this one later.
3. Neurotransmitter-Influencing Peptides
This is the category behind some of the more dramatic marketing claims.
A well-known example is:
Acetyl Hexapeptide-8
Often marketed as an “expression-line” peptide.
The idea is that it may influence neurotransmitter-related processes involved in facial muscle contraction.
This has led to marketing comparisons with injectable neuromodulators.
But we need to be very careful here.
A topical peptide serum is not Botox.
It isn’t injected into the muscle and shouldn’t be described as producing an equivalent effect.
A recent review found that acetyl hexapeptide-8 may improve wrinkle depth, hydration and elasticity in some studies, but also noted uncertainty about whether sufficient peptide reaches the neuromuscular junction to support the stronger mechanistic claims made for it.
So:
- A potentially useful cosmetic peptide? Yes.
- Topical Botox replacement? No.
4. Enzyme-Inhibiting Peptides
Some peptides are designed to influence enzymes associated with the breakdown of structural proteins.
Rather than signalling the skin to create more collagen, these peptides may aim to help reduce degradation of components such as collagen.
This category is scientifically interesting, but many claims remain more strongly supported by laboratory work than high-quality human trials.
That distinction matters.
An ingredient can have a biologically plausible mechanism without yet having extensive clinical evidence showing a meaningful visible effect in real people.
Do Peptides Actually Stimulate Collagen?
Some may.
But this is where we need to move away from treating “peptides” as one ingredient.
Specific peptides have shown effects on collagen-related pathways in laboratory and clinical studies.
Palmitoyl pentapeptide, for example, was developed specifically as a signal peptide to support collagen production and has human clinical evidence behind it.
Other peptide complexes have also demonstrated improvements in measures such as skin hydration, elasticity and dermal characteristics in clinical studies.
But we cannot take evidence from one peptide and automatically apply it to every peptide on the market.
The evidence belongs to the individual peptide or formulation studied — not to the word “peptide” as a whole.
That is probably the single most important point in this article.
Are Peptides Better Than Retinol?
Not really the right comparison.
They perform different roles.
Vitamin A has much stronger established evidence for:
- photoageing
- collagen-related changes
- fine lines
- pigmentation
- acne
- cell turnover
- Peptides
Vitamin A May support:
- signalling
- extracellular-matrix processes
- elasticity
- repair
- skin resilience
Peptides are generally less irritating than retinoids, but they also don’t have the same breadth or depth of evidence as topical retinoids.
So I wouldn’t position peptides as a replacement for Vitamin A.
They can be a very useful complement.
For someone unable to tolerate retinoids, peptides may still be worthwhile — but we shouldn’t pretend the evidence is equivalent.
Are Peptides Good for Sensitive Skin?
Often, yes.
Peptides themselves are generally not exfoliating and don’t typically produce the same irritation profile as:
- strong retinoids
- glycolic acid
- salicylic acid
- aggressive exfoliation
This can make them appealing for:
- sensitive skin
- mature skin
- compromised or recovering skin
- people who already use multiple actives
But once again, you’re not applying an isolated peptide. You’re applying a complete formulation.
A peptide serum can still contain:
- fragrance
- alcohol
- acids
- botanical extracts
- preservatives
And those things may not suit highly reactive skin.
Do Peptides Penetrate the Skin?
This is one of the genuine challenges in peptide skincare.
Peptides are often relatively large and water-loving molecules.
The stratum corneum is very effective at stopping many molecules from passing through it.
So simply putting a biologically active peptide into a serum doesn’t guarantee that meaningful amounts will reach the intended target.
Formulators may use strategies such as:
- lipid modification
- encapsulation
- carrier systems
- palmitoylation
- specialised delivery technologies to improve skin interaction or penetration.
Palmitoyl peptides are an example: attaching a fatty-acid chain can improve lipophilicity and potentially enhance interaction with the skin barrier.
Skin permeability remains an important limitation for some peptide technologies, including GHK-based peptides.
Again, formulation matters!
Why Do So Many Peptide Names Start With “Palmitoyl”?
You may see ingredients such as:
Palmitoyl Pentapeptide-4
Palmitoyl Tripeptide-1
Palmitoyl Tetrapeptide-7
The word palmitoyl means a palmitic-acid-derived lipid chain has been attached to the peptide.
This is often done to improve the peptide’s lipophilic character and its interaction with the skin.
So it isn’t merely an intimidating chemical name.
It tells us something about the way that peptide has been designed.
How Do You Find Peptides on an Ingredient List?
Unlike ceramides, peptides can appear under many different INCI names.
Some common examples include:
Palmitoyl Pentapeptide-4
Palmitoyl Tripeptide-1
Palmitoyl Tetrapeptide-7
Copper Tripeptide-1
Acetyl Hexapeptide-8
Acetyl Octapeptide-3
Tripeptide-1
sh-Oligopeptide-1
You may also see proprietary peptide complexes promoted under trademarked names.
But there’s an important warning:
Seeing five different peptides on an ingredient list does not automatically mean the serum is better than one containing two.
You still don’t know:
* the concentration
* the stability
* the delivery
* whether the individual peptides have useful evidence
* whether the formula is appropriate for your skin
Peptide counting is not a reliable way to shop for skincare.
Peptides vs Growth Factors
These categories are related conceptually but they are not the same thing.
Peptides - short chains of amino acids.
Growth Factors - larger signalling proteins involved in cellular communication, growth, repair and tissue behaviour.
Certain cosmetic peptides attempt to mimic parts of biological signalling pathways.
Growth factors themselves are much larger and biologically more complex.
We’ll cover growth factors separately later in Volume Three because they deserve their own discussion.
Peptides vs PDRN, Polynucleotides & Exosomes
Again, these are not interchangeable.
Peptides - short amino-acid chains that may influence specific signalling pathways.
PDRN / Polynucleotides - DNA-derived molecules/fragments being investigated for regenerative and tissue-repair applications.
Exosomes - Extracellular vesicles containing signalling cargo such as proteins, lipids and nucleic acids.
These may all sit under the increasingly broad umbrella of regenerative skincare, but they work through different biological mechanisms.
We should avoid calling everything “peptides” simply because it supports repair.
What About Growth-Factor Peptides?
This can become confusing because some cosmetic ingredients have names such as:
sh-Oligopeptide-1 which is associated with recombinant growth-factor technology.
Technically, these are protein/peptide-based signalling molecules, but their regulatory and biological context is different from classic cosmetic signal peptides such as palmitoyl pentapeptide-4.
What Works Well Alongside Peptides?
One of the advantages of peptides is that they are generally easy to integrate into a routine.
Ceramides - Excellent partners for maintaining a strong skin barrier.
Niacinamide - Supports barrier function and can complement peptide-based healthy-ageing routines.
Hyaluronic Acid - Provides hydration and can improve skin comfort.
Vitamin C - Can be used within the same overall routine.
Vitamin A - Often an excellent pairing.
Retinoids have strong evidence for photoageing, while peptides may provide complementary signalling and supportive functions.
PDRN / Polynucleotides - Can occupy a different regenerative role within a professionally designed routine.
Exosome-Based Skincare
Again, potentially complementary rather than interchangeable.
You don’t need to apply all of these at the same time.
Is Collagen a Peptide?
Not exactly.
Collagen is a protein, while peptides are much smaller chains of amino acids. They are closely related, but they aren’t the same thing.
A simple way to think about it is:
Amino acids → Peptides → Proteins such as collagen
Amino acids are individual building blocks.
Peptides are short chains of amino acids.
Collagen is a much larger and more complex structural protein made from long amino-acid chains organised into its characteristic triple-helix structure.
What About Collagen Peptides?
This is where the terminology can become confusing.
When collagen is broken down through a process called hydrolysis, the large collagen protein is separated into much smaller fragments. These are known as hydrolysed collagen or collagen peptides.
But the peptides commonly used in advanced skincare aren’t necessarily collagen fragments being supplied to the skin to “replace” lost collagen.
Certain cosmetic peptides are designed to act more like biological messengers or signals.
For example, some signal peptides may influence pathways involved in the production and organisation of components of the extracellular matrix, including collagen.
So when you see a skincare product described as containing “collagen-supporting peptides,” it doesn’t necessarily mean the product contains collagen.
And importantly:
Peptides don’t simply turn into collagen when you apply them to your skin.
Some are designed to signal or influence processes involved in how the skin produces and maintains its own structural proteins.
Can You Use Peptides With Acids?
Generally, yes.
The old idea that peptides instantly become “destroyed” whenever they are used anywhere near an acid is too simplistic for modern skincare formulations.
But there’s a more practical issue.
If you’re already using:
- strong AHAs
- BHAs
- retinoids
- low-pH Vitamin C
you may simply not need to layer everything into one application.
Separating products between morning and evening can make a routine simpler and more tolerable.
The goal isn’t laboratory-level ingredient gymnastics.
It’s healthy skin.
Do Peptides Replace Professional Treatments?
No.
A peptide serum may help support skin quality over time.
It cannot reproduce the biological impact of appropriately selected treatments targeting:
* collagen remodelling
* pigmentation
* vascular concerns
* acne scarring
* skin laxity
Peptides work best as part of a broader long-term strategy.
Not as a substitute for every other treatment.
The Skin Code Perspective™
Peptides are one of the skincare categories we find genuinely exciting.
But they’re also a perfect example of why ingredient education matters.
The word peptide on a bottle tells us almost nothing on its own.
At The Skin Code, we want to know:
1. Which peptide is actually being used?
2. What is that peptide designed to do?
3. What evidence exists for it?
4. How has it been formulated and delivered?
5. What else is in the formula?
6. Does the client actually need it?
We’re particularly interested in peptides as part of a broader approach to skin quality, repair, resilience and healthy ageing.
But we don’t view them as magic collagen molecules.
And we don’t believe that a serum containing ten peptides is automatically better than one containing two intelligently chosen peptides.
“Good peptide skincare isn’t about how many peptides are in the bottle. It’s about choosing the right signals — in a formulation capable of delivering them.”
Key Takeaways
✓ Peptides are short chains of amino acids.
✓ Different peptides perform different functions — there is no single “peptide effect.”
✓ Major cosmetic categories include signal peptides, carrier peptides, neurotransmitter-influencing peptides and enzyme-inhibiting peptides.
✓ Some individual peptides have human clinical evidence supporting improvements in visible signs of ageing.
✓ Evidence varies significantly between peptide technologies.
✓ Skin penetration and delivery can be major formulation challenges.
✓ Copper peptides such as GHK-Cu have particularly interesting regenerative biology, but they deserve their own detailed discussion.
✓ Peptides generally complement rather than replace Vitamin A, Vitamin C, barrier support and professional treatment.
✓ More peptides on an ingredient list do not automatically mean better results.
Not Sure Whether You Need Peptides?
If your routine already contains several serums and active ingredients, another peptide product may not necessarily be the missing piece.
Sometimes the priority is: barrier skin health
Sometimes it’s: skin rejuvenation
Sometimes it's: pigmentation correction & management
And sometimes peptides are an excellent addition.
A professional skin assessment can help determine where they actually fit rather than adding them simply because they’re currently popular.
Continue Your Skin Ingredient Journey
Next, we’ll move from signalling molecules to one of skincare’s most famous hydration ingredients — hyaluronic acid — and explore why molecular weight changes what HA can actually do in the skin.