Two melanocortin peptides
Melanotan I and Melanotan II are synthetic analogs of alpha-melanocyte-stimulating hormone (α-MSH), the endogenous ligand of the melanocortin receptor family. Both are studied in the context of melanocortin signaling, but they differ in receptor selectivity, which is the core distinction a reader should understand before comparing anything else about them.
Receptor selectivity: MC1R vs broader agonism
Melanotan I (the molecule behind afamelanotide) is relatively selective for the MC1R receptor associated with melanin-related pigment biology. Melanotan II is a less selective, more broadly acting melanocortin agonist that also engages MC4R, a receptor implicated in appetite and sexual-function pathways. This broader receptor activity is why Melanotan II is discussed in different research contexts than Melanotan I.
Approval status: a narrow authorized use
Afamelanotide (a Melanotan I peptide) has a narrow authorized medical use in some jurisdictions for a specific rare photosensitivity disorder, administered under medical supervision. That narrow approval does not extend to cosmetic use, and it does not apply to Melanotan II, which is not an approved medicine. Regulators including Health Canada have not authorized these peptides for tanning.
Why cosmetic use is unapproved and carries risk
Using melanocortin peptides to darken skin is an unapproved use that is not authorized by Health Canada, and health authorities in several countries have issued warnings about unregulated products sold for this purpose. Because these materials are typically not made under pharmaceutical standards and their effects are not established, this is an educational note on risk—this guide does not promote tanning or cosmetic use.
PT-141 and the wider family
PT-141 (bremelanotide) is a related melanocortin-pathway peptide developed along a different line, illustrating how one receptor family gives rise to compounds studied for very different purposes. Grouping these peptides by shared receptor biology, rather than by marketing narratives, is the clearest way to understand how they relate.
Sources and what they cover
These primary studies, official records and standards cover the topics linked below. The scope notes distinguish laboratory findings, human trials and regulatory records. This is a selected bibliography, not a systematic review or verification of every sentence; absence of a study here does not prove that no study exists.
- Langendonk et al. (2015) — Afamelanotide for erythropoietic protoporphyria
Clinical trial in erythropoietic protoporphyria; not evidence for cosmetic tanning or melanotan-II.
Relevant sections: Two melanocortin peptides · Approval status: a narrow authorized use
- Nelson et al. (2012) — Melanotan-II toxicity report
Individual toxicity report: demonstrates a reported risk, not its population frequency.
Relevant sections: Why cosmetic use is unapproved and carries risk
FAQ
What is the main difference between Melanotan I and II?+
Receptor selectivity. Melanotan I is relatively MC1R-selective, while Melanotan II acts more broadly across melanocortin receptors including MC4R. Their research contexts and regulatory status also differ.
Is either one approved?+
Afamelanotide, a Melanotan I peptide, has a narrow authorized medical use for a specific rare photosensitivity condition in some jurisdictions, under supervision. Melanotan II is not an approved medicine, and neither is authorized by Health Canada for tanning.
Is using these peptides for tanning safe?+
Cosmetic or tanning use is unapproved and not authorized by Health Canada, and health authorities have warned about unregulated products. This guide is educational and does not promote such use; questions about risk belong to a qualified healthcare professional.