Melanotan I and uneven pigmentation

Melanotan I can increase skin pigment, but no clinical study has shown that it produces an even cosmetic tan. A striped or patchy result cannot be diagnosed from a forum description. The safer reading is that a pigment-stimulating drug can make existing differences in skin colour more visible, while sunlight adds another uneven exposure pattern. A tan is not a substitute for sunscreen, clothing or shade.

The name also needs sorting out. Melanotan I is the research name for the alpha-melanocyte-stimulating hormone analogue later developed as afamelanotide. The licensed US product, Scenesse, is a slow-release implant used for adults with erythropoietic protoporphyria, a rare disorder that causes painful reactions to light. Its label does not cover cosmetic tanning, self-injection or products bought online^[1]. Results from that implant cannot establish the identity, purity or release profile of an unregulated vial.

Why pigment can look uneven

Afamelanotide binds mainly to melanocortin 1 receptors and increases production of eumelanin, a brown-black form of melanin, without needing sunlight or artificial ultraviolet light^[1]. That does not mean every patch of skin will finish at the same colour. Baseline pigment, freckles, moles and ultraviolet exposure already vary across the body. The Scenesse label warns that its pharmacological effect can cause general skin darkening as well as darkening of existing moles and freckles. It recommends a full-body skin examination twice a year to monitor old and new pigmented lesions^[1].

A small prospective study gives a closer look at those focal changes. Researchers followed 15 adults with erythropoietic protoporphyria who received two afamelanotide implants and examined 103 acquired moles with a dermatoscope. At five months, existing moles showed changes including focal thickening of the pigment network and more pigmented globules. The changes had returned to baseline by 12 months. The investigators did not see new moles or dermoscopic signs suggesting malignant transformation^[2]. This is reassuring within that small, medically supervised group. It also shows why a pigment agonist need not change every part of the skin uniformly.

What the human tanning trials found

An older controlled study enrolled 65 fair-skinned volunteers and administered the same synthetic peptide by injection for three 10-day cycles over three months. Melanin density rose across eight measured skin sites. The average increase was 41% in volunteers whose skin had a low minimal erythema dose, meaning it burned with less ultraviolet exposure, compared with 12% in those with a higher minimal erythema dose^[3]. The study also reported fewer sunburn cells and less thymine-dimer formation after a controlled ultraviolet challenge in the low-threshold group^[3].

Those findings are often stretched too far. The trial measured pigment and laboratory markers after a defined experimental product. It did not test whether participants could stop using sunscreen, whether cosmetic colour stayed even, or whether unknown online products prevented skin cancer. The licensed label is equally narrow: Scenesse is indicated to increase pain-free light exposure in adults with erythropoietic protoporphyria, not to prevent ordinary sunburn in people seeking a tan^[1].

Why a darker colour does not replace sun protection

Ultraviolet rays can damage skin cells even when skin does not look burned. The US Centers for Disease Control and Prevention says most skin cancers are caused by too much ultraviolet exposure and advises a combination of shade, protective clothing and broad-spectrum sunscreen^[4]. Pigmentation may change how quickly visible redness appears, but colour is not a dose meter for ultraviolet injury. Deliberately adding sun exposure to chase a more even result adds a known source of skin damage.

This is also where related peptides can cause confusion. PT-141, or bremelanotide, is another melanocortin agonist, but it is a different medicine with a different indication. Prior use of tirzepatide does not tell us why pigmentation changed. No study cited here tested melanotan I after major weight loss, alongside an incretin medicine, in older adults with loose or folded skin. Grouping all of those details into one explanation would be guesswork.

What to do with a new pigment pattern

A new uneven pattern deserves a pause, not a home experiment to even it out. Stop using the appearance of the tan as a guide to further exposure. Photograph the area in neutral light so changes can be compared, and arrange a clinician or dermatologist review if a mole or patch is new, changing, asymmetric, irregular at the border, varied in colour, or otherwise concerning. The Scenesse label's monitoring warning applies to a regulated implant under clinical care^[1]. It is a reason for more caution with an unverified product, not less.

PeptideMethods does not recommend melanotan I for cosmetic tanning and does not provide a dose or schedule. If you are considering any melanocortin product, discuss the product, the reason for using it and any pigment changes with a qualified healthcare professional. Continue ordinary sun protection regardless of how dark the skin looks.

What we do not yet know

There is no verified explanation for the striped result that prompted this article. The available human studies do not isolate skin folds, age-related texture, weight loss or previous GLP-1 and GIP treatment as causes of uneven melanotan-related pigmentation. The mole study included only 15 patients, and its reassuring 12-month findings cannot rule out uncommon or long-term harms^[2]. We also cannot transfer a licensed implant's safety record to a product whose contents and manufacturing history are unknown.