Acetyl hexapeptide-8 vs Hexapeptide-9
It is a cream ingredient sold as a needle-free way to smooth expression lines. Two small trials disagreed: one showed less wrinkling, one showed none. It is put in anti-ageing creams to smooth wrinkles. The one controlled trial, of 96 adults, tested a changed version and was run by a cosmetics company.
Acetyl hexapeptide-8 has the stronger evidence, grade B (some human evidence) against grade C for Hexapeptide-9. Neither is FDA approved.
Evidence
BSome human evidence
CAnimal and cell studies
Human studies cited
Animal or cell studies cited
Why the grade
For wrinkle reduction there is one randomized placebo-controlled trial in 60 Chinese adults showing a benefit, a 19-person split-face double-blind study showing none, a 26-patient uncontrolled series and the manufacturer's original volunteer study. Skin penetration work in human and animal skin finds very little of the peptide reaches the dermis, which leaves the mechanism in doubt. Small samples and conflicting results keep this at B.
For wrinkle reduction, the evidence for standard hexapeptide-9 is unpublished supplier data, lab and mouse work, and a small split-face volunteer test of a delivery carrier. The one randomised double-blind trial, published in 2025 by employees of a cosmetics company, enrolled 96 adults but tested a chemically modified cyclised version against a low-concentration retinol and vehicle over 56 days, so the standard ingredient stays at C.
FDA
Cosmetic ingredient
Acetyl hexapeptide-8 (Argireline) is a cosmetic ingredient, and the FDA does not approve cosmetic ingredients before sale; products containing it are regulated as cosmetics so long as they claim only to improve appearance. It is not an approved drug for any use.
Cosmetic ingredient
Hexapeptide-9 is a cosmetic ingredient. Cosmetics do not go through FDA drug approval, so it has no approved indication and makes no drug claims; it is listed under its INCI name in skincare formulations.
Sold for
Argireline is marketed as a needle-free alternative to Botox that relaxes expression lines when applied as a cream or serum.
Hexapeptide-9 is marketed in anti-aging serums as a collagen fragment that signals skin cells to rebuild the dermis and smooth wrinkles.
Studies say
One small randomized trial found a measurable reduction in eye-area wrinkles and another found none, while penetration studies show almost none of the peptide reaches the muscle layer, so the evidence supports a modest surface effect at best (grade B).
The only controlled human trial tested a modified molecule and was run by the manufacturer, and the data for standard hexapeptide-9 are laboratory assays, so the grade is C.
Class
Neurotransmitter-inhibiting peptide
Signal peptide
Route
Topical
Topical