Walk into any Sephora and you'll see peptides everywhere: Matrixyl serums, Argireline eye creams, copper peptide masks. Search for peptides online and you'll find injectable protocols for BPC-157, GHK-Cu, and Thymosin Beta-4. The word "peptide" covers both categories, and the confusion between them is costing women money, time, and realistic expectations.
This glossary decodes every peptide you're likely to encounter — from drugstore serums to functional medicine clinics — so you can evaluate claims in either context.
Cosmetic peptides: what's on the label
These peptides are formulated into topical skincare products. Their mechanism of action is limited by skin penetration — most peptides are too large to pass through the stratum corneum efficiently, so their effects are concentrated in the outer skin layers.
Matrixyl (Palmitoyl Pentapeptide-4)
The most-studied cosmetic peptide. Matrixyl mimics a collagen fragment that signals fibroblasts to produce new collagen and fibronectin. Clinical studies show measurable reduction in wrinkle depth after 2-4 months of twice-daily application. The effect is real but modest — comparable to a good retinol, not to injectable collagen stimulation. Also sold as Matrixyl 3000 (which combines two peptides) and Matrixyl Synthe'6 (six-peptide blend).
Argireline (Acetyl Hexapeptide-3)
Marketed as "topical Botox." It targets SNAP-25, a protein involved in neurotransmitter release at the neuromuscular junction. In theory, reducing SNAP-25 activity reduces muscle contraction and softens expression lines. In practice, topical application delivers minimal peptide to the muscle layer. Studies show modest wrinkle reduction — but the Botox comparison is marketing fiction, not pharmacological reality.
SNAP-8 (Acetyl Octapeptide-3)
An extended version of Argireline with the same mechanism but reportedly greater potency. The evidence base is thin — primarily manufacturer-sponsored studies. If Argireline is a gentle breeze, SNAP-8 is a slightly stronger gentle breeze. Neither is a storm.
Copper Peptides (GHK-Cu in cosmetic form)
GHK-Cu appears in both worlds. In cosmetic serums, it's applied topically at low concentrations. The copper tripeptide stimulates collagen synthesis, promotes wound healing, and has antioxidant properties even at the topical level. Of all cosmetic peptides, copper peptide serums have the strongest evidence bridge to the research compound — because GHK-Cu is the same molecule whether you apply it to your face or inject it subcutaneously. The difference is penetration depth and concentration.
Leuphasyl (Pentapeptide-18)
Targets the enkephalin pathway rather than the SNAP-25 pathway. Marketed for expression lines, often combined with Argireline. Limited independent evidence.
Palmitoyl Tripeptide-1 / Palmitoyl Tetrapeptide-7 (Matrikines)
Signal peptides that mimic collagen and elastin fragments. Used in "firming" formulations. The evidence is mostly manufacturer-produced, and independent verification is limited.
Acetyl Tetrapeptide-5 (Eyeseryl)
Targets under-eye puffiness through reducing glycation and improving lymphatic drainage. Small manufacturer studies show modest effects on periorbital edema. Not widely studied independently.
Research and therapeutic peptides: what's in the vial
These peptides are administered by injection (subcutaneous, intramuscular), nasal spray, or oral capsule. Their effects are systemic or tissue-level, not surface cosmetic.
GHK-Cu (injectable form)
The same copper tripeptide in your serum, but delivered systemically at higher concentrations. Injectable GHK-Cu influences over 4,000 genes related to tissue remodeling, inflammation, and DNA repair. The skin effects are tissue-deep: collagen and elastin production, improved wound healing, hair follicle support. This is the bridge compound — same molecule, different delivery, dramatically different depth of effect.
BPC-157
A 15-amino-acid peptide derived from gastric juice. Research focuses on gut barrier repair, tendon healing, and anti-inflammatory effects. Not a cosmetic peptide — its relevance to women's health is in gut healing (IBS, endometriosis-related GI symptoms) and surgical recovery.
Growth Hormone Secretagogues (Sermorelin, CJC-1295/Ipamorelin, Tesamorelin)
Stimulate growth hormone production. GH supports collagen synthesis, fat metabolism, sleep quality, and tissue repair. The skin effects are a downstream benefit of improved GH levels, not a direct peptide-to-skin mechanism like GHK-Cu.
PT-141 (Bremelanotide)
The only peptide FDA-approved specifically for women — treats hypoactive sexual desire disorder (HSDD) in premenopausal women. Works on melanocortin receptors in the brain, not on the skin. Not a cosmetic peptide by any definition.
How to evaluate peptide skincare claims
Check the ingredient concentration. Peptides are effective above certain concentrations. Many serums list peptides as the 10th or 15th ingredient, meaning they're present at trace levels that may not produce the effects shown in studies. Studies typically test at 1-5% concentrations; consumer products may contain far less.
Look for independent studies. Manufacturer-sponsored studies are not worthless, but independent replication is the standard for confident claims. Matrixyl and GHK-Cu have the most independent evidence. Many newer cosmetic peptides rely entirely on in-house data.
Compare cost to alternatives. A $120 peptide serum that produces results comparable to a $20 retinol is not a better product — it's a more expensive path to the same outcome. Peptide skincare makes the most sense when it provides benefits that retinoids, vitamin C, or niacinamide don't (which is rare for most cosmetic peptide formulations).
Don't confuse categories. A serum containing "peptides" does not deliver the effects described in peptide therapy literature. Your Matrixyl serum does not stimulate growth hormone. Your Argireline eye cream does not heal your gut. The categories share a word, not a mechanism.