What it is
Melanotan II (MT-II) is a lab-made peptide modeled on alpha-melanocyte-stimulating hormone (α-MSH), the natural signal that tells skin cells to make more melanin (pigment). It was originally developed at the University of Arizona in the 1980s-90s as a potential 'sunless tanning' agent, on the theory that boosting pigment could darken skin and reduce sun damage.
It is important to be clear: Melanotan II is not an approved drug in the US, UK, EU, or Australia. It is sold on the internet and in some gyms as an unlicensed injectable or nasal product, and is marketed to researchers as a powder 'for laboratory research use only.' Products bought this way are unregulated, and analyses of illegally sold vials have found inconsistent purity and dosing.
MT-II is closely related to two other compounds: afamelanotide (Melanotan I), an FDA-approved implant for a rare light-sensitivity disorder, and bremelanotide (Vyleesi), an approved treatment for low sexual desire. MT-II itself was never brought to market.
How it works
Melanotan II is a non-selective agonist of the melanocortin receptors (MC1, MC3, MC4, and MC5). Activating the MC1 receptor on pigment cells (melanocytes) stimulates production of melanin, which is what produces the tanning effect. Because it acts through the body's own pigment machinery, the tan can develop with less UV exposure than normal.
Because MT-II is non-selective, it also switches on receptors unrelated to tanning. Activation of the MC4 receptor in the brain is thought to drive its well-known side effects on sexual function and appetite, including spontaneous erections in men and reduced hunger. In plain terms, a peptide aimed at skin color also affects the brain and other systems, which is a large part of why its side-effect profile is broad.
What people research it for
Skin tanning / increased pigmentation
Early human dataThis is the effect MT-II is best known for. A small pilot Phase-I study in three men found measurable increases in facial, upper-body, and buttock pigmentation after low subcutaneous doses. This is a researched effect, not a safety endorsement.
Reduced UV needed to tan
Preclinical / theorizedBecause pigment is stimulated directly, users may darken with less sun exposure. This has been proposed as a theoretical way to reduce sunburn, but protection against skin cancer has never been demonstrated in humans.
Erectile / libido effects
Early human dataTrial subjects experienced spontaneous erections lasting 1-5 hours. This unintended finding led to the separate development of the approved drug bremelanotide for sexual dysfunction.
Appetite suppression
Animal studiesMelanocortin (MC4) signaling reduces appetite in animal models, and reduced hunger is anecdotally reported by users. This is not an approved or validated use.
What the research actually shows
Human evidence for MT-II is thin. The main data come from a 1996 pilot Phase-I study in a handful of subjects, which showed it can produce tanning but also documented nausea and the spontaneous-erection effect. There have been no large randomized trials of MT-II for tanning, no long-term safety studies in healthy adults, and no controlled data on whether it raises or lowers melanoma risk.
Regulators have gone the other direction and actively warned against it. The UK's MHRA has warned the public not to use Melanotan, closed down supplier websites, and logged reports of suspected side effects including stomach, heart, blood, and eye problems. Cancer Research UK and health agencies in the EU, US, and Australia have issued similar cautions, noting the products are illegal to sell and of unknown safety.
By contrast, the related peptide afamelanotide (Melanotan I) went through full trials and is FDA-approved for erythropoietic protoporphyria, and bremelanotide is approved for sexual desire disorder. MT-II sits outside all of that: an unapproved compound whose known effects come mostly from a tiny early trial plus a scatter of adverse-event case reports.
Research handling & storage
In research settings, Melanotan II is supplied as a white lyophilized (freeze-dried) powder in a sealed vial. It is reconstituted with bacteriostatic or sterile water before use in a lab, and the resulting solution is typically kept refrigerated. As a peptide, it is sensitive to heat, light, and repeated freeze-thaw cycles.
Sealed lyophilized vials are generally stored frozen or refrigerated and are more stable than reconstituted solution, which degrades faster and is usually used within a few weeks. Because MT-II is not a licensed medicine, no pharmacy-grade quality control applies to material sold online, and independent testing has found counterfeit and impure product; this is handling context for research material, not a preparation guide for human use.
Safety & cautions
Melanotan II has genuine, documented risks and no approved safety margin. The most consistently reported side effects are nausea, facial flushing, and spontaneous, sometimes prolonged erections (priapism), which was seen even in the original clinical trial.
The most serious concern is pigment-related: MT-II causes darkening of existing moles and freckles, and multiple published case reports describe moles changing during or shortly after use, including cases of melanoma (a life-threatening skin cancer) arising from such lesions. Whether MT-II directly causes melanoma or simply coincides with heavy UV/sunbed use is still debated, but the changing-mole signal is real and alarming, and it can also mask the warning signs dermatologists look for.
On top of the drug itself, self-injecting unregulated product carries infection and contamination risks, and regulators including the MHRA, FDA, and Australia's TGA have issued explicit warnings against using it. Anyone who has used it and notices a mole change should see a dermatologist promptly.
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Frequently asked questions
Is Melanotan II FDA approved?
No. Melanotan II is not approved by the FDA or by any regulator in the UK, EU, or Australia, for tanning or anything else. It is sold illegally online and marketed as 'research only.' The MHRA and other agencies have publicly warned people not to use it.
Is Melanotan II safe?
Its safety is unknown and there are real documented risks: nausea, facial flushing, prolonged erections, darkening and changes in moles, and reports of side effects affecting the stomach, heart, blood, and eyes. It has never passed the trials required to establish safety, so it should not be considered safe.
Can it cause melanoma or change my moles?
It reliably darkens existing moles, and several published case reports describe moles changing during use, including melanoma developing from those lesions. It is not proven that the peptide directly causes melanoma, but the mole changes are documented and concerning, and they can also hide the visual warning signs of skin cancer. Anyone noticing a changing mole should see a dermatologist.
How is it different from afamelanotide or bremelanotide?
Afamelanotide (Melanotan I) and bremelanotide are both FDA-approved drugs that went through full clinical trials for specific conditions. Melanotan II is a related but separate, unapproved compound that never reached the market.
Why is it sold as 'for research use only'?
Because it isn't an approved medicine, vendors label it as a laboratory research chemical rather than something for people to take. That label does not make it tested, pure, or safe for human use.
Sources
- MHRA / regulatory warning against Melanotan tanning injections (Cancer Research UK)
- Evaluation of melanotan-II in a pilot Phase-I clinical study (PubMed)
- Changes of melanocytic lesions induced by Melanotan injections — case report (PMC)
- DermNet: Melanotan II overview and risks
Last reviewed 2026-07-07. This guide is educational and research-focused — not medical advice. Melanotan II products referenced on PeptidePub are sold by third parties as materials for laboratory research use only, not for human or animal consumption.
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