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 You Should Avoid Using Nasal Tanning Sprays Fake tanning Melanoma Fund UK Melanotan II an overview ScienceDirect Topics Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn