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 Targeting the central melanocortin system for the treatment of metabolic disorders Nature Reviews Endocrinology View of Association of tanning injection with hypercortisolism, hyperglycaemia and ketosis in type 1 diabetes mellitus British Journal of Diabetes Nasal tanning sprays linked to skin cancer, trading standards officers warn Consumer affairs The Guardian