Melanotan II: Tanning injections, nasal sprays harmful to health Imagine just wanting to be jacked and tan and you end up like this? Melanotan II is a peptide that increases the melanin in your skin and can give men a boner that 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 Pyoderma Gangrenosum Secondary to Melanotan Cureus