# Melanotan 2: A Plain-English Review of the Pigmentation Research > Melanotan 2 is a synthetic melanocortin peptide studied for skin darkening in small early human trials. A patient, cited walkthrough of the melanogenesis evidence. A calm, plain-English reading of the melanogenesis literature — what the pigmentation studies measured, what people report, and what to watch out for, with every claim cited. ## Start here Melanotan 2 is a lab-made copy of a natural body signal called alpha-MSH (a hormone that tells skin cells to make pigment). It is best known for one thing: it can darken skin with little or no sun. In a small early study, low doses given under the skin made two of three volunteers visibly tanner without UV light (Dorr 1996) [1]. People also report less appetite, a strong rise in sex drive, and — in men — spontaneous erections, because the same family of receptors it switches on sits in the brain too. None of this is approved medicine. Melanotan 2 has never passed full human testing and is not approved anywhere for any use. It is sold online as an unlicensed tanning injection, and real harms — darkening and changing moles, kidney injury, prolonged painful erections, and nausea — show up in published case reports. This site is a reading list of that research, not a sales page and not medical advice. What people report, including the downsides, is laid out plainly on [the effects page](/effects). ## What the research has actually shown Melanotan 2 (also written Melanotan II or MT-2) is a cyclic seven-amino-acid peptide built at the University of Arizona in the late 1980s to be a stronger, longer-lasting version of the body's own pigment hormone, alpha-MSH (alpha-melanocyte-stimulating hormone) [3]. Chemists closed it into a small ring, which makes it both more potent and harder for the body to break down quickly. The pigmentation finding is the one that started everything. A pilot Phase I study in three healthy men escalated subcutaneous (under-the-skin) doses from 0.01 to 0.025-0.03 mg/kg every other weekday for two weeks; two of the three developed visibly darker facial, upper-body, and buttock skin after just five low doses, with no UV exposure (Dorr 1996) [1]. That is a study-design fact, not a dosing instruction — and Melanotan 2 is not approved for human use. The same study turned up the effects that made the peptide famous for other reasons: spontaneous erections lasting one to five hours, mild nausea, and at the top dose, daytime sleepiness [1]. Those non-skin effects trace back to the brain, which we cover on [Melanotan 2 effects](/effects). ## Why one peptide darkens skin and changes appetite at the same time The short answer is that Melanotan 2 is not selective. It switches on all five melanocortin receptors (MC1R through MC5R), and those receptors do very different jobs in different parts of the body [3]. In the skin, switching on MC1R tells pigment cells (melanocytes) to make more of the dark, protective pigment called eumelanin — the engine of the tan. In the brain, switching on MC4R turns down appetite and turns up sexual signaling, which is why users so often report eating less and a sharp jump in libido. One molecule, several switches, several effects. The plain-English mechanism walkthrough lives on [what is melanotan 2](/what-is-melanotan-2), and the receptor-by-receptor detail is in the [Melanotan 2 research](/research). ## What people report — the good and the unwelcome Beyond the lab, a real-world picture has built up from people who self-inject Melanotan 2 to tan. The benefits they describe are a faster, deeper tan with far less sun, reduced appetite, and a strong libido boost. The downsides they describe are just as consistent: nausea, facial flushing, a flu-like run-down feeling in the first days, and — the one that sends people to a doctor — moles getting darker and new moles appearing. These accounts are anecdotal, not clinical evidence, and we keep them clearly separate from the cited studies. We have collected them, with the published safety cautions alongside, on the [Melanotan 2 effects](/effects) page. If you read only one page here, read that one. ## How to read this site Think of these pages as a guided tour of the evidence, in plain language. [What is melanotan 2](/what-is-melanotan-2) explains the molecule and how it works. [Melanotan 2 tanning](/tanning) digs into the pigmentation studies specifically. [Effects](/effects) covers reported benefits, side effects, and safety. The [research](/research) page is the deeper science with full citations, and [dosage](/dosage) explains what was studied in trials and animals — as research facts, never as a how-to. Every number you read here maps to a real study in the [Melanotan 2 references](/references). --- A patient walkthrough of the melanocortin pigmentation literature — a reading guide, not a clinic, a vendor, or a tanning product.