Argireline, properly acetyl hexapeptide-8, is a six amino acid cosmetic peptide. Its mechanism is often described as a topical alternative to botulinum toxin, and the underlying idea is loosely related: it is thought to interfere with the protein complex that helps nerve cells release the signal telling muscles to contract. The comparison collapses on contact with reality. Botulinum toxin is injected directly into muscle and blocks that signalling potently, while argireline is applied to the skin surface, where it must first cross a barrier specifically evolved to keep molecules out. The measurable effect is modest and the evidence comes largely from small cosmetic studies. It is a real ingredient with a real, small effect, sold under an oversized comparison.