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 Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn Burning for a Tan: Why Sunbeds and Melanotan Aren't Worth the Risk Young Scot Dangerous' tanning products promoted by influencers Teen Boys and Young Men Are Injecting Peptides in Search of Perfection WSJ