# Melanotan 2 Side Effects: What the Research Shows > Melanotan 2 side effects from the literature and user reports: nausea, flushing, darkening moles, and the serious documented adverse events. Cited throughout; not medical advice. ## The gist This page sorts the Melanotan 2 side effects into two honest groups. First, the common, mostly short-lived effects that almost everyone who uses it describes: nausea, facial flushing, an odd urge to stretch and yawn, tiredness, and — relevant to this site — moles and freckles going darker. Second, the rare but serious effects that have been published as medical case reports: melanoma and atypical moles, kidney and muscle injury, prolonged painful erections, and a brain-swelling syndrome. We label which is which, because they are not the same kind of evidence. The common effects come from what users report; the serious ones come from doctors' published cases. And because the products are unregulated, some 'side effects' may really be reactions to contaminants. Nothing here is dosing or medical advice. ## The common, transient side effects **These are effects reported by the research-use community and noted in the small studies — anecdotal where described by users, not clinical proof. No doses are given.** The most consistent is **nausea**, sometimes with vomiting, usually within the first hour of a dose and worst in the early days; in the controlled studies it was dose-related and was severe in roughly 13% of subjects at 0.025 mg/kg [25]. **Facial flushing** and a hot sensation come on within minutes to an hour. A distinctive **urge to stretch and yawn** repeatedly is frequently described soon after dosing — it appeared even in the controlled erectile-dysfunction trial, where stretching and yawning were noted alongside nausea [2]. A flu-like **fatigue** in the first days is common enough to have a nickname ('melanotan flu'). Because the compound is injected, **injection-site reactions** — redness, itching, bruising, small lumps — are commonly reported. Most of these ease as use continues, though not for everyone. ## The pigment side effects this site focuses on Several side effects are pigment-related, and they are the reason a skin-focused digest treats this compound seriously. Users very commonly report **existing moles and freckles darkening**, often before the overall tan even develops, with spots standing out sharply against the skin. Many report the appearance of **brand-new moles**, sometimes within a day or two of a dose — the published literature contains exactly such a case, with eruptive nevi and darkening of pre-existing nevi within 24 hours of a single injection [5]. Users also describe **selective darkening of lips, gums, scars, and genital and underarm skin**, and a recent case report documented reversible brown pigmentation of the gums and inner cheeks in a man who injected the compound over 64 days, with the cheek pigment fading after stopping while the gum pigment lingered [37]. The overall tan itself often arrives **uneven or blotchy** and **fades slowly and patchily** over weeks to months after stopping. ## The serious, documented adverse events These are not common, but they are published, and they are severe. **Melanoma and atypical (dysplastic) moles** have been reported in users [4][7][8][9], with dermoscopy showing change in lesions during use [10] and one high-genetic-risk patient developing a dysplastic nevus after combining the compound with sunbed use [11]. **Rhabdomyolysis with systemic toxicity** [14] and **renal infarction** [15] have each been reported, indicating potential muscle and kidney injury. **Priapism** — a prolonged, painful erection that is a urological emergency — has been reported several times, including after overdose [16][17][18]. **Posterior reversible encephalopathy syndrome (PRES)**, a reversible brain-swelling condition, has been reported once in association with use [19]. The plausible thread through the vascular events is a pressor effect documented preclinically for melanocortin agonists [20][21]. Any of these warrants immediate medical attention. ## Side effects versus contaminants One reason the side-effect picture is murky is that much of what users inject is not pure Melanotan 2. Analytical studies of online products repeatedly find mislabeling, variable peptide content, and impurities [12][24], and the substance appears in surveys of falsified injectables [26]. Some reactions attributed to the compound may therefore be reactions to contaminants, wrong doses, or non-sterile material. This is also why side-effect reports from unregulated use cannot be read as a clean safety profile for the molecule itself — and why the [melanotan 2 dangers](/dangers) page treats unknown product content as a hazard in its own right. Melanotan 2 holds no regulatory approval, and these effects are documented in the context of unsupervised use [29]. --- A measured digest of the published record on Melanotan 2 — an archive to be read, not a remedy to be followed.