Melanin: Skin, Hair & Eye Pigment – Types, Benefits & Genetics

Melanin is a natural polymer pigment produced by melanocytes in the basal layer of the epidermis. It determines the color of skin, hair, and eyes and provides critical photoprotection.

Two Primary Types

Type	Color Range	Key Features
Eumelanin	Brown, black, dark brown	High photostability; superior UV shielding; dominant in darker skin/hair.
Pheomelanin	Red, yellow, pink	Less photostable; generates reactive oxygen species under UV; dominant in red hair, fair skin, freckles.

Genetic & Environmental Control

• Genetics: MC1R (melanocortin-1 receptor) variants strongly influence eumelanin/pheomelanin ratio. Other genes (TYR, OCA2, TYRP1) modulate total melanin output.
• Sun exposure: UVR upregulates melanogenesis via MSH/α-MSH signaling → tanning (delayed pigment darkening).

Protective Functions

• UV screening: Melanin granules form "supranuclear caps" over keratinocyte nuclei, absorbing/scattering UV photons.
• Free-radical scavenging: Neutralizes ROS generated by UV, reducing DNA damage and lipid peroxidation.
• Thermoregulation: Contributes to heat dissipation.

Clinical Relevance

• Low eumelanin → higher risk of sunburn, photoaging, melanoma, non-melanoma skin cancers.
• Albinism (genetic melanin deficiency) → profound photophobia, nystagmus, high skin-cancer risk.
• Melasma, post-inflammatory hyperpigmentation → localized melanin overproduction.

Melanin is thus both a cosmetic determinant and a vital biological shield.