Tanning injections come in two forms: melanotan I and melanotan II. Both types of injections work by replicating alpha-melanocyte-stimulating hormone in your body. This hormone binds to melanocortin receptors and stimulates the production of melanin in skin cells. The more melanin your skin cells produce, the darker your skin will be.
Melanotan I lasts longer in your body than Melanotan II before being broken down by enzymes. Melanotan I is medically known as afamelanotide.
Melanotan II binds to a wider range of receptors than melanotan I and has a shorter lifespan in your body. It can also cross your blood-brain barrier, leading to side effects such as loss of appetite, sexual dysfunction, and fatigue. Melanotan II is not currently used to treat any disease.