melanin

Melanin is a pigment that is ubiquitous in nature, being found in most organisms. In animals melanin pigments are derivatives of the amino acid tyrosine.

The most common form of biological melanin is eumelanin. Another common form of melanin is pheomelanin, a cysteine-containing red-brown polymer of benzothiazine units largely responsible for red hair and freckles.

The increased production of melanin in human skin is called melanogenesis. The photochemical properties of melanin make it an excellent photoprotectant.