Melanotan-1

People run it for one thing: a tan that comes from inside the skin rather than the sun, plus the photoprotection that comes with it. It pushes the skin to produce eumelanin, so users report tanning faster and burning less for the same sun exposure. As a regulated drug it's used for a rare light-sensitivity disease (erythropoietic protoporphyria, EPP) — the community tanning use borrows that biology off-label.

The single most useful thing to understand about this peptide is that it is NOT the one most people mean. Melanotan-1 is MC1R-selective — it hits the pigment receptor and essentially nothing else. Melanotan-2 is non-selective and also lights up MC3R and MC4R, which is where the libido, spontaneous-erection and appetite-suppression effects come from. So if a "tanning peptide" is giving someone those effects, they're on MT-2, not MT-1. The community signal is consistent on this: MT-1 users report the tan without the nausea-and-arousal rollercoaster, at the cost of MT-1 being slower and milder.

A linear, MC1R-selective analogue of α-melanocyte-stimulating hormone ([Nle4-D-Phe7]-α-MSH). Activating MC1R on melanocytes shifts pigment production toward eumelanin — the dark, photoprotective form — which is what increases tanning and raises the threshold for phototoxic/burn reactions. Because it is selective for MC1R and does not meaningfully engage MC3R/MC4R, it lacks the central libido and appetite actions that define MT-2.

The defining one is darkening and possible enlargement of existing moles and freckles — this is the side effect that matters most, because it can mask or mimic the kind of change a dermatologist watches for. Beyond that: mild flushing right after injection and dose-dependent nausea, both usually manageable by dosing lower. Note that nausea here is mild and pigment-pathway-adjacent, NOT the libido/appetite cluster — if someone is getting strong nausea, spontaneous erections or appetite loss, that points to MT-2, not MT-1. The honest unknown is long-term safety of chronic off-label use: the clinical safety record is for the EPP implant under medical supervision, not for years of self-injected research-grade powder.

Not a stack component in any community protocol — it's run on its own for pigment. The only pairing people mention is behavioral, not pharmacological: still using real sun (or a minimal UV trigger) to actually express the tan, and watching their skin. It does NOT belong in the same conversation as MT-2 or PT-141 even though all three are melanocortin peptides; the receptor selectivity is the whole point of choosing MT-1.