What are the mechanism of action and side effects of Melanotan 2 (afamelanotide)? Your body already makes a hormone that tells your skin to tan. Melanotan 2 is a synthetic peptide engineered to mimic that hormone but in a version that's more potent and longer lasting than Warning issued over increased use of 'Barbie drug' Don't risk your health for a summer glow! Tanning nasal sprays are creeping onto the UK market, particularly on online and lack of regulation means they are a significant risk to your Melanotan II Wikipedia