Acetyl hexapeptide-8 vs Palmitoyl pentapeptide-4
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-wrinkle creams, often under the name Matrixyl, to smooth fine lines. One trial of 93 women showed a small gain, but the maker ran it and no one else has repeated it.
Both sit at grade B: some human evidence. Neither is FDA approved.
Evidence
BSome human evidence
BSome human evidence
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.
One randomized, double-blind, placebo-controlled split-face trial in 93 women showed a measurable reduction in fine lines and wrinkles over 12 weeks, backed by a 1993 cell study identifying the five-amino-acid sequence as a stimulator of collagen production. The trial was run by the manufacturer and has not been independently replicated, which caps it at B.
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
Palmitoyl pentapeptide-4 is a cosmetic ingredient, sold under trade names such as Matrixyl. It is not approved by the FDA as a drug for any use; the FDA regulates cosmetics but does not approve their ingredients.
Sold for
Argireline is marketed as a needle-free alternative to Botox that relaxes expression lines when applied as a cream or serum.
Palmitoyl pentapeptide-4, better known as Matrixyl, is the peptide most anti-wrinkle creams point to when they say peptides work.
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).
A single sponsor-run randomized trial found modest wrinkle improvement versus the same moisturizer without the peptide, which is better evidence than most cosmetic peptides have and still short of independent confirmation.
Class
Neurotransmitter-inhibiting peptide
Signal (collagen) peptide
Route
Topical
Topical