Peptides

Peptides are short chains of amino acids. Researchers sort cosmetic peptides into four groups: signal peptides that 'message' skin cells, carrier peptides that deliver trace elements such as copper, neurotransmitter-inhibiting peptides aimed at expression lines, and enzyme-inhibiting peptides that slow the enzymes that break skin proteins down [1].

The best-known signal peptide is palmitoyl pentapeptide-4, sold as Matrixyl. A palmitic acid tail is added to help it reach skin and resist breakdown [2]. In placebo-controlled, split-face studies of 28 to 93 people over 28 days to 4 months, it reduced measured wrinkle depth and roughness [1][2]. Many of these trials were run by or for ingredient makers, and several tested formulas that also contained niacinamide and vitamins, so the peptide's own effect isn't always clear [1].

Argireline (acetyl hexapeptide-8) mimics a fragment of SNAP-25, a protein involved in muscle signalling [6]. In one trial, 45 people using a 10% Argireline product for four weeks had a 48.9% reduction in measured eye-area fold depth, against no change in the 15 on placebo [3]. Lab tests found less than 0.2% of applied Argireline crossed the skin's outer layer in 24 hours [6], which is why 'Botox in a bottle' is marketing.

Copper peptide (GHK-Cu) occurs naturally in blood plasma, and levels fall with age [4]. Twelve-week studies reported denser, firmer-looking skin and softer fine lines [4], but the lead review author is linked to a company selling GHK-Cu products.

The big picture is modest. A 2026 meta-analysis pooled 19 randomised trials, but only two (105 people) were topical; their effect on wrinkles was smaller than for oral peptides and not statistically significant. Peptides were well tolerated, with minimal side effects [3].