No, you don't need the 'Barbie drug' to tan, whatever TikTok says. Here's why melanotan II is so risky 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 Eruptive naevi and darkening of preexisting naevi 24 h after a single mono dose injection of melanotan II Semantic Scholar Melanotan II Safety: Tanning Injection LIVV Natural Cancer Association of South Africa (CANSA) Fact Sheet and Position Statement on Sunless Tanning