Acetyl tetrapeptide-15 is a synthetic peptide used in the cosmetics for sensitive skin. Acetyl tetrapeptide-15 is derived from endomorphin-2 (Tyr-Pro-Phe-Phe-NH2), a human μ-opioid agonist with selective anti-nociceptive effect. Acetyl tetrapeptide-15 reduces skin hyperreactivity producing inflammatory, chronic and neuropathic pain, by increasing the threshold of neuronal excitability in μ-opioid receptor via an endorphin-like pathway.