Experts lash use of popular social media sun tanning drug Melanotan Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn 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 Barbie drug' nasal spray tan plugged by influencers causes cancer, doctors warn