The safety record
Changing moles and reported harms
The colour that starts the story can also make it troubling. The consequences described in people are unsettling, even while the biology intrigues me.
New and changing moles
A report of eruptive dysplastic nevi describes multiple new and changing moles after melanotan use, with abnormal features on tissue examination. Another case report documents melanoma associated with Melanotan II use. These reports give the concern a concrete clinical record.
The review of unregulated alpha-MSH analogue use gathered reports of changes in existing moles, newly emerging nevi and melanoma, while explicitly stating that a causal link was unproven. That uncertainty pulls at me from both directions. It leaves a risk question open and leaves the reported cases on the record.
The early chemoprevention proposal looks bleaker against this later record. The proposed preventive purpose cannot do the work of a long-term safety study.
A conflicting preclinical direction
The literature also contains a topical Melanotan II study in melanoma cells and mice. It reported inhibited cell migration and invasion and attenuated established tumour progression in the mouse model, with a proposed MC1R-related mechanism involving PTEN.
I resisted this paper at first because it disturbed a tidy safety narrative. It deserves to disturb it. A topical experiment in cells and mice, and case reports involving people, investigate very different circumstances. I can take the preclinical finding seriously while leaving the human safety question unresolved. The useful response is to specify the route, model and outcome, then ask how those differences affect the biology.
Pigmentation beyond the skin surface
A 2026 oral-mucosa case report describes brown pigmentation of the gums and inner cheek in a man who self-administered Melanotan II. Cheek pigmentation began fading by 28 days after cessation; gum pigmentation remained at reduced intensity at 3 months. The different course at the two sites is striking.
The mouth is an awkward place for a story about choosing a cosmetic colour to end up. The pigmentation described in that case extended to sites far from the imagined sunlit face. A case report cannot supply a frequency, but its particulars widen the question about where an effect can appear.
Kidney injury, muscle injury and priapism
The reported harms reach beyond pigment. A renal infarction case and literature review describes a possible association with Melanotan II. A separate systemic-toxicity report describes rhabdomyolysis, severe muscle breakdown, and acute kidney injury requiring intensive care after a high self-administered dose.
A priapism report after Melanotan II overdose adds prolonged erection to that record. A frequency calculation is beyond what these reports can supply. The case reports establish that serious outcomes were documented; they leave important questions about causation, susceptibility and frequency.
Contents and anecdotal accounts
In an analytical study of online Melanotan II preparations, measured peptide content ranged from 4.32–8.84 mg against a stated 10 mg. Samples from two of the three shops contained unidentified impurities at 4.1–5.9%. These were findings about the analysed samples. The samples give a glimpse of uncertain contents; extending that glimpse to every preparation would stretch it too far. It does make the preparation itself an additional uncertainty.
A qualitative study of online discussions identifies nausea, flushing and changes in skin lesions among the reported concerns. Those forum accounts are anecdotes, not clinical evidence of how common an effect is. The published analysis helps describe what people were discussing; it cannot convert a discussion into a controlled safety result.