Melanotan II is a synthetic analog of alpha-MSH, the hormone that tells your melanocytes to produce melanin. Inject it and your skin tans. That is the simple version. The full version involves four other hormone receptors and a side effect profile that is more interesting than the marketing suggests.
What it actually is
Melanotan II was developed in the 1980s and 1990s at the University of Arizona, originally as a way to induce protective tanning in fair-skinned populations and reduce skin cancer risk. The original idea was sound: people who tan well get less melanoma; if you can produce a tan without the UV exposure that drives skin cancer, you have a useful drug. The molecule worked. Commercialization fell apart for various reasons, and Melanotan II was never approved anywhere.
A more selective derivative called afamelanotide, marketed as Scenesse, did make it through approval for a rare condition called erythropoietic protoporphyria. Scenesse hits the melanocortin-1 receptor with much less crosstalk to the other melanocortin receptors that Melanotan II activates. That selectivity is the difference between a clean tanning effect and the full Melanotan II side effect profile.
How it works
Melanotan II is a non-selective melanocortin receptor agonist. It hits all five of them. Each receptor does something different.
MC1R is the tanning receptor. Activation tells melanocytes to ramp up production of eumelanin, the dark protective pigment. The tan is real, not cosmetic. It builds over a few weeks of dosing and lasts for a few months after you stop, depending on UV exposure during and after.
MC4R controls appetite, libido, and erections. Activation suppresses appetite and produces spontaneous erections in men. The latter effect was strong enough that a related compound called bremelanotide was developed and eventually approved (as Vyleesi) for hypoactive sexual desire disorder in women.
MC3R is involved in metabolism and inflammation. MC5R is involved in sebum production by skin glands. The full constellation of effects from non-selective agonism is the reason Melanotan II produces side effects that pure MC1R agonists do not.
Side effects
Nausea is the big one. Most users report it at the start of every dose, fading after about 30 minutes. Facial flushing is universal. Spontaneous erections in men are common enough to be a punchline in the relevant subreddits. Blood pressure can shift in either direction, sometimes meaningfully. Appetite tends to drop, and in some users this is significant enough to cause unintentional weight loss.
Dosing schedules typically start with a loading phase of 0.25 to 1mg subcutaneously, repeated every other day until a tan develops, followed by maintenance dosing once or twice weekly. The loading phase is where most of the side effects cluster.
The mole problem
Increased melanocyte activity does not happen only in the melanocytes you want darkened. It happens in every melanocyte you have. New moles appear. Existing moles darken and sometimes change shape. This is a documented effect, and it is the reason dermatologists are not fans.
There are case reports of melanoma in users of Melanotan II, though no causal study has confirmed the link. The mechanistic story is plausible enough that taking the drug while also chasing UV exposure is something almost no oncologist would sign off on. Anyone using Melanotan II should have a baseline full-body skin check before starting and follow-up checks regularly during use.
Status
Not approved anywhere. Sold openly in some European markets, illegally in others, and through grey-market channels in the United States. Quality varies, and counterfeit product is common. There is essentially no GMP supply available.
The honest closing
Melanotan II works. It produces a tan that is photoprotective in a real biological sense. It also produces a mole-and-melanocyte-activity profile that warrants serious dermatological monitoring, particularly if you are also chasing sun exposure to make the tan darker. The risk-reward case is best for users with very pale Fitzpatrick I skin who want photoprotection and who commit to dermatology screening, and worst for users with existing dysplastic nevi or family history of melanoma.
See it on you
PepScan shows what Melanotan II tanning could actually look like on your specific complexion. Results vary substantially by baseline skin type, which is why a generic before-and-after image is not very useful. Snap one photo and you get a projection calibrated to your skin.