The colouration of the skin is provided by melanin.
Melanin is a complex polymer derived from the amino acid tyrosine. Melanin is responsible for determining skin and hair colour and is present in the skin to varying degrees, depending on how much a population has historically been exposed to the sun.
Melanin is found in:
- The skin where it provides skin colour
- Pupils or irises of the eyes
- Stria vascularis of the inner ear
- Areas of the brain, the substantia nigra and locus coeruleus
- The medulla and zona reticularis of the adrenal gland
Types of Melanin
- Eumelanin makes mostly dark colours in hair, eyes, and skin. There are two types of eumelanin: brown and black. Black and brown hair come from different mixes of black and brown eumelanin.
- Pheomelanin colours the pinkish parts of your body, like the lips and nipples. You get red hair when you have the same amount of pheomelanin and eumelanin.
- Neuromelanin Controls the colours of neurons. It isn’t involved with the colouring of things you see.