Dangerous 'Barbie drug' Melanotan II sparks crackdown on social media influencers ABC News Here's the part nobody explains when they're selling you the "Barbie drug.", Melanotan 2 is a synthetic peptide that mimics alpha MSH a hormone your body already makes to tell your skin cells to Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn Melanotan II PERMANENTLY Darkened My Skin!