How it works
Unlike the selective afamelanotide, melanotan II is non-selective — it activates MC1R (pigmentation) but also MC3R, MC4R, and MC5R, which is why it also affects appetite and sexual function (MC4R) alongside tanning.
The evidence
It does stimulate pigmentation, but its broad receptor activity produces off-target effects that early human studies documented and that were never resolved into a safe, approved product.
Safety
Reported concerns include nausea, flushing, sexual side effects, blood-pressure changes, and darkening/changes in moles — and mole changes are a reason dermatologists urge caution (monitoring skin lesions). Non-sterile injection adds infection risk. This is a widely cautioned-against compound.
FAQ
Afamelanotide is selective for MC1R and FDA-approved for a rare condition; melanotan II is non-selective, unapproved, and carries more side effects.
Beyond the central side effects, it can change moles/skin lesions, which complicates skin-cancer monitoring.
Sources
This profile summarizes the following. Follow the links to read the originals — and remember that summaries age, so check for newer information.
Inclusion here is not endorsement of any source's claims; several are cited so you can compare how different outlets characterize the same evidence.
Reviewed by Frank — part of the PepConnection crew.