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 The peptide revolution: inside the injectables industry You may have heard about the latest trend tanning nasal sprays and injections. So how does it work and is it safe? Refs: Fjellhaugen Hjuler et al., 2014, Melanoma associated with the use of Understanding Peptides: