Peptides are short chains of amino acids — the building blocks of proteins like collagen, elastin, and keratin. In skincare, they act as signaling molecules: small enough to penetrate the skin's surface and communicate with cells to trigger specific biological responses. The category is large and uneven — some peptides have strong clinical backing, others are mostly marketing.
How Peptides Work
There are several mechanisms depending on the type. Signal peptides (like Matrixyl/palmitoyl pentapeptide-4) mimic fragments of broken-down collagen, signaling skin to produce more. Carrier peptides deliver trace minerals like copper or manganese that are required for collagen synthesis. Neurotransmitter-inhibiting peptides (like Argireline/acetyl hexapeptide-3) reduce muscle contraction — a topical alternative to botulinum toxin, though far milder in effect. Enzyme-inhibiting peptides slow down the enzymes that break down collagen (matrix metalloproteinases).
Peptides With Real Evidence
- Palmitoyl pentapeptide-4 (Matrixyl) — one of the most studied; increases collagen I, III, and IV in multiple trials
- Matrixyl 3000 (palmitoyl tripeptide-1 + palmitoyl tetrapeptide-7) — combination shown to reduce wrinkle depth
- Copper peptides (GHK-Cu) — wound healing, collagen stimulation, anti-inflammatory; strong evidence base
- Acetyl hexapeptide-3 (Argireline) — modest muscle-relaxing effect in repeated expressions; best around eyes
- Palmitoyl tripeptide-38 — newer, shown to boost multiple ECM proteins
- Leuphasyl + Argireline combination — stronger evidence for expression line reduction than either alone
The Concentration Problem
Most peptide products are underdosed. Effective clinical concentrations for Matrixyl are typically 3–8 parts per million — which sounds tiny but is the validated range. When a peptide appears near the bottom of an ingredient list, it's often present as a marketing ingredient. Look for products where 2–3 peptides appear in the middle of the list, or brands that publish their peptide concentrations. The Ordinary and NIOD (both from Deciem) are unusual in disclosing concentrations.
How to Layer Peptides
Peptides are compatible with almost everything. Apply after cleansing and toning, before heavier moisturizers. Avoid using copper peptides at the same time as vitamin C (ascorbic acid) — copper oxidizes ascorbic acid, reducing both ingredients' efficacy. Use them at different times of day. Peptides work well with niacinamide, hyaluronic acid, and ceramides. They complement retinol — alternating nights or using in the morning while retinol is at night is a solid approach.
Realistic Expectations
Peptides are not botulinum toxin and will not replicate its results. They are supportive anti-aging ingredients — working over months to preserve and modestly improve skin structure. They shine in combination routines rather than as solo hero ingredients. The best case for peptides: consistent use over 3–6 months as part of a routine that also includes SPF and (if tolerated) retinol. On their own, expect subtle rather than dramatic change.