What are Melanotan I and Melanotan II?
Both peptides are lab-made versions of alpha-melanocyte-stimulating hormone (alpha-MSH), a natural hormone that tells skin pigment cells to make melanin. Researchers at the University of Arizona developed them in the 1980s and early 1990s to darken skin without sun exposure, with the idea that this might help protect against sun damage. Natural alpha-MSH breaks down very quickly, so both were designed to last longer.
Melanotan I was later developed as afamelanotide. It was approved in the US in 2019 as Scenesse, a small implant placed under the skin, for adults with erythropoietic protoporphyria (EPP), a rare genetic condition that makes light exposure painful. Melanotan II was never approved as a medicine anywhere. The melanotan products sold online for tanning are unlicensed, and their contents are not checked.
How do Melanotan I and II work?
Both activate melanocortin receptors. MC1R, found on pigment cells, drives the production of eumelanin, the darker brown-black pigment. Melanotan I's main known effects come through MC1R, so they center on pigment. Melanotan II strongly activates several melanocortin receptors, including MC3R and MC4R in the brain. MC4R is involved in sexual function and appetite, which is thought to explain why Melanotan II can cause erections and reduced appetite in addition to tanning.
What has research looked at?
- Light sensitivity in EPP
- In clinical trials in people with EPP, afamelanotide increased the time people could spend in light without pain and improved quality of life compared with placebo. This is the basis of its approved use.
- Vitiligo
- A small trial reported that afamelanotide with light therapy sped up repigmentation in some people with vitiligo, compared with light therapy alone.
- Sun protection
- Both peptides darkened skin in early studies, but that darkening has not been shown to protect against skin cancer.
- Erections and libido
- Small University of Arizona trials in men with erectile dysfunction reported erections with Melanotan II. This work led to bremelanotide (PT-141) rather than to an approved Melanotan II.
The evidence for the two is very different. Melanotan I, as afamelanotide, has clinical trial data for one rare disease. Melanotan II has small early human studies and a growing number of case reports from unlicensed use. Neither has been shown to be safe or useful for cosmetic tanning.
Melanotan I vs Melanotan II
Melanotan I is a straight chain of 13 amino acids. Its effects center on skin color, and as afamelanotide it became an approved medicine. Melanotan II is a shorter, ring-shaped peptide that acts on several melanocortin receptors, including ones in the brain. Its effects are broader, with more reported side effects such as nausea, flushing and unwanted erections.
Side effects and cautions
Health agencies in several countries have warned against unlicensed melanotan tanning injections and nasal sprays. Their concerns include unknown contents, contamination, unsterile products and infection risk from injecting. Known side effects include nausea, flushing, fatigue, yawning and, with Melanotan II, spontaneous and sometimes prolonged erections. The biggest concern is the skin. Anyone with moles, skin changes or a history of skin cancer should talk to a qualified clinician.
- Moles and skin cancer
- Users have reported new moles and darkening or changing existing moles, and doctors have published case reports of melanoma in people using melanotan. These reports do not show that melanotan causes melanoma, but darker moles can make warning signs harder to spot.
- Added UV exposure
- Some users pair melanotan with sun or sunbed exposure, which adds UV damage to the skin.
- Prolonged erections
- Priapism, an erection that will not go away, has been reported with Melanotan II and is a medical emergency.
- Blood pressure and other serious events
- Melanocortin agonists can raise blood pressure. Isolated case reports have described serious problems, such as kidney damage and muscle breakdown, in people using Melanotan II.
Further reading
This page summarizes the research in plain words. To read the studies yourself:
- Published studies on Melanotan I and Melanotan II PubMed, US National Library of Medicine
