Peptides in skincare: What do they actually do and do you need them?

Peptides are everywhere in skincare right now.

They’re talked about alongside collagen, firmness, smoother skin and skin longevity, and they’re increasingly appearing on the front of products rather than being hidden away in an ingredient list.

But what exactly are peptides? What are they actually doing when you apply them to your skin? And should you care whether your skincare contains them?

The short answer is: potentially, yes. But not simply because a product says “with peptides”.

We asked Consultant Dermatologist Dr Clare Kiely to break down what actually matters.

What are peptides and what do they actually do?

At their simplest, peptides are short chains of amino acids - the building blocks our bodies use to make proteins.

Collagen is one of those proteins.

But what makes certain peptides interesting in skincare isn’t simply what they’re made from. It’s how they can interact with biological processes already taking place within the skin.

“Some peptides can act as signalling molecules,” explains Dr Kiely. “They can interact with pathways that are already present in the skin, which is why particular peptides can be selected for very particular jobs.”

And that is an important distinction, because “peptide” isn’t one ingredient doing one thing.

There are hundreds of cosmetic peptides available, with different functions. Some are associated with signalling processes involved in collagen and the extracellular matrix. Others may act as carriers, interact with enzymes or influence completely different processes within the skin.

“Simply knowing that a product contains peptides doesn’t really tell you enough,” says Dr Kiely. “The more useful questions are: which peptide, why has it been included, and what has the finished product actually been shown to do?”

Think of it a little like seeing “vitamins” written on a label. Your next question would probably be: which ones?

Peptides should be approached in much the same way.

Do peptides help with collagen and skin ageing?

This is probably where most of the interest in peptides comes from.

Collagen is one of the major structural proteins within the dermis and plays an important role in the skin’s strength and support.

As we age  and particularly as a result of cumulative UV exposure the balance between collagen production and breakdown changes. 

But collagen doesn’t work in isolation. It sits within a much larger structural network known as the extracellular matrix, or ECM, which also includes elastin, fibrillin and other molecules involved in the skin’s resilience and organisation.

Certain peptides are designed to interact with signalling pathways involved in this wider system.

“When we talk about peptides in the context of skin ageing, we’re often interested in how they communicate with pathways associated with collagen and the extracellular matrix,” says Dr Kiely. “It isn’t a case of putting collagen back into the skin. We’re looking at how we can support the skin’s own biological processes.”

So rather than thinking of peptides as replacement collagen, it may be more useful to think of certain peptides as messengers, helping to send or reinforce particular signals within the skin.

Over time, where a formulation is effective, those biological changes may translate into the things we actually notice in the mirror: smoother-looking skin, improved firmness or elasticity and a reduction in the appearance of fine lines.

Peptides are therefore much more about supporting skin quality over time than producing an instant tightening effect.

Are all peptides the same?

Definitely not.

“Peptide” describes an enormous family of molecules, which means two products can both claim to contain peptides while using completely different ingredients for completely different reasons.

And more isn’t necessarily better.

“Five peptides aren’t automatically better than two,” says Dr Kiely. “What matters is whether a peptide has been selected for a clear purpose, whether it works within that formulation and whether there is evidence supporting the claims being made.”

That’s why simply counting how many peptides appear on a label isn’t particularly helpful.

A carefully selected peptide in a well-designed formulation may be far more meaningful than a long list of fashionable ingredients added primarily for marketing appeal.

Can peptides get where they need to go? 

This is one of the most important and often overlooked parts of the conversation.

Skin is very good at its job. Its outer layers are specifically designed to keep things out.

So choosing an interesting active ingredient is only one part of making an effective skincare product. Scientists also have to consider its stability, how it behaves within the formula and whether it can reach the relevant site within the skin.

“An ingredient appearing on the INCI list doesn’t necessarily tell us whether enough of it can reach where it needs to act,” Dr Kiely explains. “Delivery is a really important part of formulation.”

Peptides can be particularly challenging because of their molecular characteristics.

One approach is to attach a lipid component to the peptide. You may have noticed the word palmitoyl before certain peptide names on an ingredient list. This changes the peptide’s physical properties and can make it more suitable for topical delivery.

Another approach is encapsulation, where an ingredient is housed within a microscopic delivery system, such as a liposome, which can help protect it and support delivery.

All of which means an ingredient list can only ever tell you part of the story.

So when choosing peptide skincare, look beyond the word “peptides” on the label and consider whether there is a clear reason for their inclusion and evidence that the finished formulation actually works.

The bottom line

Peptides can be extremely interesting skincare ingredients, but the word itself is not a guarantee of efficacy. Different peptides do different things. Delivery matters. Formulation matters. And testing the final product matters.

As Dr Kiely puts it:

“Consumers shouldn’t have to become cosmetic chemists to choose effective skincare. Ultimately, the simplest question is still probably the most useful one: has the product actually been shown to do what it says it does?”

And in an increasingly noisy skincare space, that may be the question worth asking more often.