Peptides are one of those skincare categories where the gap between evidence and marketing is particularly wide. The word “peptide” on a label signals sophistication and science, but there are hundreds of peptides with vastly different functions and evidence bases. A few are among the best-studied actives in cosmetic dermatology. Many are present in products at concentrations too low to do anything meaningful. Knowing which ones are worth seeking out changes how useful peptide-containing products are in your routine.
What peptides are
Peptides are short chains of amino acids. Two amino acids linked together form a dipeptide; up to about 50 amino acids in a chain forms a peptide; longer chains are proteins. In the body, peptides function as signalling molecules: they communicate between cells, trigger specific cellular responses, and regulate biological processes including collagen synthesis, wound repair, and enzyme activity.
In skincare, peptides are used either to mimic naturally occurring cellular signals (stimulating collagen or elastin production), to inhibit certain enzyme activities (blocking muscle contraction in the case of so-called “Botox peptides”), or to support the skin barrier through structural means.
The theoretical appeal is strong. If you can trigger the same cellular response that would be triggered by the body’s own signalling molecules, you can influence skin behaviour in specific ways without the harsh side effects that come from more aggressive actives.
The absorption challenge
The primary limitation of topical peptides is penetration. The skin barrier is specifically designed to prevent large molecules from passing through, which creates a challenge for all topical actives but is particularly relevant for peptides, which are larger than most other skincare actives.
Research into peptide delivery has focused on solutions to this: using very short peptides (two to four amino acids) that are smaller, modifying peptides with lipid groups to make them more lipid-soluble, and formulating in vehicles that facilitate penetration. The most widely used peptides in skincare are specifically selected or designed with this challenge in mind.
Peptides with substantial evidence
Palmitoyl pentapeptide-4 (Matrixyl) is probably the most studied cosmetic peptide. It’s a synthetic peptide developed by Sederma that stimulates collagen I, III, and fibronectin synthesis. Multiple independent studies have shown improvements in wrinkle depth with consistent use. A 2005 study in the International Journal of Cosmetic Science found significant reductions in crow’s feet depth after 28 days. It’s used at concentrations of 3-8 ppm in formulas, and the research is consistently more credible than most peptide marketing.
Matrixyl 3000 is a blend of palmitoyl tetrapeptide-7 and palmitoyl oligopeptide, also developed by Sederma. It works on hyaluronic acid production in addition to collagen stimulation. The company has conducted clinical studies showing improvements in wrinkle appearance, and independent researchers have validated some of these findings.
Argireline (Acetyl hexapeptide-3 or acetyl hexapeptide-8) is the peptide marketed as “Botox in a bottle.” It inhibits the SNARE complex, which is involved in the neuromuscular signal that causes muscle contractions. This is the same mechanism as botulinum toxin, but at a very localised, surface level rather than injected into the muscle. The evidence shows modest reductions in expression lines with consistent use. This is real but much less dramatic than injectable treatments, and it’s a realistic rather than revolutionary benefit.
Copper peptide (GHK-Cu, glycine-histidine-lysine copper complex) has decades of research behind it, making it one of the oldest cosmetic peptides. It stimulates collagen and glycosaminoglycan synthesis, has antioxidant and anti-inflammatory properties, and appears to promote wound healing. The research base is unusually broad and includes studies outside of commercial interests.
Palmitoyl tripeptide-5 stimulates TGF-beta (transforming growth factor beta), which triggers collagen production through a different pathway than Matrixyl. Some formulators use it alongside Matrixyl to stimulate collagen through two complementary mechanisms.
What often doesn’t work despite the label
Many peptides are present in products at concentrations that are cosmetically meaningless. An ingredient appearing at position eighteen on a twenty-ingredient label is there in a very small amount. Peptides are expensive, so formulations designed for cost rather than efficacy will include them for marketing while keeping concentrations below what any research has shown to be effective.
Peptides can also break down in formulas if not properly stabilised. Some peptides are unstable in the presence of certain preservatives, acids, or when exposed to air. A peptide serum that was effective at manufacturing might be degraded by the time it’s used if it’s not properly formulated for stability.
How to use peptides
Apply peptide serums after cleansing and any water-based actives, before heavier creams. Peptides work best at neutral to slightly acidic pH, which means they shouldn’t be applied immediately after a low-pH vitamin C or AHA product. Either use them at a different time of day or wait a few minutes between application.
They can be used morning and evening. Unlike retinol, they don’t increase photosensitivity. Unlike AHAs, they don’t exfoliate. They’re compatible with most other ingredients and can run as a consistent background active alongside more intensive actives used at specific times.
HOIA’s Anti-Aging Face Serum includes plant-based actives alongside supporting ingredients for collagen and elasticity, formulated for consistent evening use as part of a targeted anti-ageing approach. For anyone in their mid-thirties and beyond looking to build a more active skincare routine, peptides in a well-formulated serum are one of the more evidence-supported options alongside vitamin C and retinol.