Narrower indications

• Photoageing — 1 graded row from 2 compounds checked
• Skin laxity — 0 graded rows from 3 compounds checked
• Facial wrinkles — 3 graded rows from 8 compounds checked

Compounds with a graded row

Ordered by rung, strongest first. The rung rates the study design; the chip beside it says what the study measured. Both are needed.

1. Collagen Peptides

   human RCT Direct outcome Not approved for this condition

   Who was studied

   healthy adults, both sexes, n=70, oral 1,650 mg/day low-molecular-weight collagen peptide, 8 weeks plus 2-week washout

   A randomised, double-blind, placebo-controlled trial of an oral collagen peptide measured facial wrinkle depth, height and visual severity, elasticity (R2/R5/R7), hydration and dermal density, and reported improvement against placebo. A 2026 systematic review and meta-analysis of 19 randomised trials (n=1,341) found only a modest pooled wrinkle effect, driven by oral rather than topical peptides. This is oral exposure only; nothing here supports a topical collagen peptide product.

   Source PubMed 2 primary sources read for this row

2. Hexapeptide-9

   human RCT Direct outcome Not approved for this condition

   Who was studied

   adult men and women with ageing skin, n not reported in the abstract; topical 0.002% serum twice daily, 56 days

   A randomised, double-blind, vehicle- and active-controlled 56-day trial of a topical 0.002% cyclized hexapeptide-9 serum measured crow's feet and forehead wrinkle number, area and roughness against a 0.002% retinol serum and vehicle, and reported larger reductions than retinol on all measured outcomes except crow's feet roughness. The tested material is a cyclized variant, not plain hexapeptide-9, and the enrolled number was not reported in the abstract.

   Source DOI 1 primary source read for this row

3. Palmitoyl Pentapeptide-4 (Matrixyl)

   human RCT Direct outcome Not approved for this condition

   Who was studied

   Caucasian women aged 35-55, n=93, topical (3 ppm pal-KTTKS in a moisturiser), 12 weeks, split-face left-right randomised

   A 12-week double-blind, split-face, randomised comparison of a moisturiser with and without 3 ppm palmitoyl pentapeptide-4 measured wrinkles and fine lines by image analysis and expert grading, and reported improvement versus the placebo side. It is a single cosmetic-industry trial in one narrow population; no independent replication is on file, and the peptide is a cosmetic ingredient with no regulatory approval for any skin condition.

   Source DOI 1 primary source read for this row

4. Argireline (Acetyl Hexapeptide-3)

   human observational Direct outcome Not approved for this condition

   Who was studied

   adult women, n=19, topical hyaluronic acid serum with and without Argireline applied to opposite sides of the face, 4 weeks

   A double-blind, within-subject split-face study measured facial wrinkle scores by Visia imaging after 4 weeks and found no statistically significant reduction on the Argireline side. Randomisation of side allocation was not reported, so this is graded below human_rct despite the vehicle control. This is the only controlled human wrinkle study of Argireline alone located; every other human study of it is a multi-ingredient formulation from which the peptide's own contribution cannot be separated.

   Source PubMed 1 primary source read for this row

5. GHK-Cu

   in vitro Mechanistic only Not approved for this condition

   Who was studied

   cultured human dermal fibroblasts and UV-damaged human skin biopsy tissue ex vivo; no living human or animal subjects

   Recorded, and not evidence for this condition

   This is the same molecule the source names by its INCI name, copper tripeptide-1, and the same single study: elastin expression, elastase inhibition and elastic-fibre architecture in fibroblast culture and ex vivo UV-damaged human skin. No study measured a skin-ageing outcome in humans — no wrinkle, elasticity or photographic measure was taken in any living person, and no trial of topical or injected GHK-Cu for skin ageing is on file. The connection to skin ageing rests entirely on fibroblast and ex vivo elastin expression and is a mechanistic argument, not a result; a 2025 review of topically applied GHK states plainly that clinical studies are absent.

   Source DOI 2 primary sources read for this row

Checked, and nothing recorded

14 compounds were checked against skin ageing and produced no gradeable row.

• Acetyl Tetrapeptide-11 — checked, no row on file
• Acetyl Tetrapeptide-5 — checked, no row on file
• Acetyl Tetrapeptide-9 — checked, no row on file
• Dipeptide Diaminobutyroyl Benzylamide Diacetate — checked, no row on file
• Elastin Peptides — checked, no row on file
• Hexapeptide-11 — checked, no row on file
• Palmitoyl Hexapeptide-12 — checked, no row on file
• Palmitoyl Tetrapeptide-7 — checked, no row on file
• Palmitoyl Tripeptide-1 — checked, no row on file
• Pentapeptide-18 — checked, no row on file
• Silk Peptides — checked, no row on file
• Soy Peptides — checked, no row on file
• Tetrapeptide-21 — checked, no row on file
• Tripeptide-10 Citrulline — checked, no row on file

A compound is here because someone looked and the sources did not support a row — not because nobody looked. Under the rubric, uncertainty resolves to no row, and a row resting on a vendor page or a clinic blog is worse than no row at all.