Melanin

What Is Melanin?

Melanin is the primary pigment responsible for the colour of human skin, hair, and eyes. It is produced by specialised cells called melanocytes, located in the basal layer of the epidermis. Melanin is synthesised through a biochemical pathway called melanogenesis, beginning with the amino acid tyrosine and regulated by the enzyme tyrosinase. Beyond colour, melanin serves a critical photoprotective function: it absorbs and dissipates UV radiation as heat, protecting underlying cells from DNA damage.

The Two Types of Melanin

Eumelanin is the dark, brown-black pigment dominant in darker skin tones and brown/black hair. It provides stronger UV photoprotection. Pheomelanin is the yellow-red pigment more abundant in people with red hair and fair skin. It provides less UV photoprotection and paradoxically can generate ROS under UV exposure, potentially contributing to photocarcinogenesis. Most people produce a mixture of both types, with the ratio determining overall skin tone.

Melanin Transfer and Distribution

Melanocytes produce melanin in organelles called melanosomes, which are then transferred to surrounding keratinocytes via dendritic processes — one melanocyte supplies approximately 36 keratinocytes. In lighter skin tones, melanosomes are smaller and clustered; in darker skin tones, they are larger and individually distributed. This distribution pattern, along with melanin quantity, determines UV protection level — not melanocyte number, which is roughly equal across all skin tones.

See Melanogenesis and Hyperpigmentation.