Melanotan II is a lab-made peptide — a short chain of amino acids — built as a copy of the natural hormone alpha-MSH. It is best known as a "tanning injection" because it makes skin darker, and it is a close cousin of the approved peptide PT-141. But the honest headline matters up front: Melanotan II is not an approved medicine anywhere, and the human record is a series of case reports flagging real harms — changing moles and melanoma, prolonged painful erections, and frequent nausea15.
In plain terms: an unapproved gray-market peptide with a genuine mechanism and a genuinely worrying safety trail. This page explains what it is and what the literature reports — not how to use it.
What it is
Melanotan II is a cyclic peptide — a looped chain, which makes it sturdier than a straight one — modeled on alpha-melanocyte-stimulating hormone (alpha-MSH)3. Alpha-MSH is the body's master melanocortin signal, controlling pigment, appetite, and arousal.
It is often confused with two other things:
- Afamelanotide (Scenesse) is a *different*, regulated melanocortin drug used under medical supervision for a rare light-sensitivity disorder. Melanotan II is not that.
- PT-141 (bremelanotide) is Melanotan II's approved cousin, but it is more selective for brain receptors. Melanotan II is non-selective — it hits the skin pigment receptor hard as well4.
How it works: hitting every melanocortin lock
Melanocortin signals act through receptors named MC1R through MC5R — five "locks," each opening a different door. Melanotan II is a broad agonist (a key that turns locks *on*), and unlike the more targeted PT-141 it turns several at once:
- MC1R on skin pigment cells — this is the tanning door. Switching it on tells pigment cells to make more melanin, darkening the skin even without much sun4.
- MC3R and MC4R in the brain — the appetite-and-arousal doors. This is why users report reduced appetite and spontaneous erections3.
In plain terms: PT-141 mostly presses the brain buttons; Melanotan II presses the brain buttons *and* the skin-pigment button. That extra pigment-cell stimulation is exactly what raises the melanoma concern below.
Pharmacokinetics: what little is known
Here honesty is required: Melanotan II's human pharmacokinetics — how fast it is absorbed and cleared — are poorly characterized, because it never went through the formal drug-development studies that measure this. The natural hormone it mimics, alpha-MSH, breaks down in the body within minutes; Melanotan II was designed to be more stable and longer-acting, but reliable half-life figures in humans are not well established3. Treat any specific number you see quoted as an estimate, not a measured fact.
| Property | Detail |
|---|---|
| Class | Synthetic cyclic peptide analogue of alpha-MSH |
| Targets | Melanocortin receptors, non-selectively — MC1R (skin pigment), MC3R/MC4R (brain) |
| Route in reports | Subcutaneous injection (also nasal sprays on the gray market)3 |
| Human half-life | Not well characterized; formal PK data lacking3 |
| Reported effects | Skin darkening, appetite suppression, spontaneous erections, nausea, flushing3 |
| Regulatory status | Not approved anywhere; FDA and TGA warnings4 |
What the studies actually found
There are no controlled efficacy trials of Melanotan II. What exists instead is a scatter of case reports and reviews — and, importantly, much of it is about *harm*, not benefit. Here is the record, oldest to newest:
| Study | Model | Key result | Year |
|---|---|---|---|
| Paurobally et al.1 | Human case report | Melanoma developed at a changing pigmented mole after Melanotan use; authors urged caution | 2011 |
| Hjuler & Lorentzen2 | Human case report | Cutaneous melanoma reported in a young woman after Melanotan II plus tanning-bed use | 2014 |
| Brennan et al. — review3 | Review of use + outcomes | Catalogued unregulated use and adverse effects: nausea, flushing, changing moles, contamination of product | 2014 |
| Habbema et al. — review4 | Review | Summarized risks of unregulated alpha-MSH analogues, including dysplastic/atypical nevi and product-quality problems | 2017 |
| Mallory et al.5 | Human case report | Ischemic priapism — a painful erection lasting about 30 hours — after a self-administered injection, needing surgical treatment | 2021 |
| Oral-mucosa case6 | Human case report | Pigmentary changes in the mouth lining associated with Melanotan II injections | 2026 |
The pattern is the opposite of a reassuring one: the human literature is dominated by things that went wrong. That does not mean every user is harmed — case reports capture the people who ended up in front of a doctor. But it does mean the documented human evidence leans toward risk, not benefit.
Honest limitations and safety
This is the section that matters most for Melanotan II. The concerns below are drawn from peer-reviewed reports and reviews.
Moles and melanoma
Because Melanotan II directly stimulates pigment cells (MC1R), dermatologists worry it could drive existing moles to change or new atypical moles to appear. Multiple case reports describe exactly that — darkening moles, new dysplastic (atypical) moles, and melanoma diagnosed after use12. Reviews treat this as a real, biologically plausible concern and recommend skin monitoring4.
Priapism
Because it activates the brain arousal pathway, Melanotan II can cause unwanted, prolonged erections. A published case describes ischemic priapism — a painful erection lasting roughly 30 hours after a self-administered injection — that required surgical intervention5. Untreated priapism is a urological emergency.
Nausea and other effects
Nausea is one of the most commonly reported effects, alongside facial flushing and spontaneous erections3. Reviews also document rarer serious reports and, critically, that gray-market product is often unregulated, mislabeled, or contaminated — so what is in a vial may not match the label at all4.
Not approved — and regulators have said so
Melanotan II is not approved as a medicine in any major jurisdiction. Regulators including the U.S. FDA and Australia's TGA have specifically warned consumers against it4. This page takes no position on sourcing and never discusses where to obtain anything — it simply reports the regulatory reality.
Latest research
- Newer case reports keep appearing, including a 2026 report of pigmentary changes in the lining of the mouth linked to Melanotan II injections — a reminder that the pigment effect is not limited to skin6.
- The evidence type has not changed. Even as reports accumulate, there is still no controlled human efficacy trial; the literature remains case reports and reviews, which is itself the key honest finding4.
We keep this section current as new reports land — and for Melanotan II, "new report" has usually meant a new safety signal.
The short version
Melanotan II is a non-selective copy of the hormone alpha-MSH that darkens skin by switching on pigment cells and raises arousal through brain receptors. It is not approved anywhere, its human pharmacokinetics are barely characterized, and the peer-reviewed human record is dominated by harm — melanoma and changing moles, prolonged painful erections, and nausea. The honest evidence label is unapproved, with real safety signals. For its regulated, brain-selective cousin, see PT-141 (bremelanotide); for the wider context, the research peptides overview.