Pigment

Pigment (from the Latin pigmentum Farbe, make-up) in the narrower medical sense of the word refers to the (endogenous) colouring substances that occur in human cells and tissues, especially in the skin and skin appendages (hair, nails) in dissolved or nodular form.

In humans, the most important endogenous pigments are melanin, haemoglobin and its derivative haemosiderin, as well as bile dyes. In their composition and density, together with the blood circulation of the skin, they define the individual skin colour.

In principle, pigments can be divided (in the medical-cosmetic field) into:

• biogenic pigments and
• non-biogenic technical pigments

can be subdivided.

Biogenic pigments are coloring compounds that determine the physiological skin color of humans or change it artificially.

Non-biogenic, technical pigments are finely dispersed (insoluble in a medium) organic (e.g. acid dyes as insoluble metal salts) or also inorganic dyes (e.g. titanium dioxide).

Biogenic pigments can be divided into endogenous biogenic pigments and exogenous biogenic pigments.

• Endogenous biogenic pigments are melanin, hemoglobin, myoglobin, lipofuscin, biliverdin, bilirubin, and hemosiderin (see also under hyperpigmentation).
• Exogenous biogenic pigments enter the body from outside. Exogenous biogenic pigments include coal dust, metal dust, ink (e.g., introduced into the skin by tattooing ), and e.g., the orally ingested carotenoids or certain drugs (e.g., amiodarone -see also amiodarone hyperpigmentation).

Non-biogenic technical pigments are finely dispersed organic (e.g. acid dyes as insoluble metal salts) or inorganic dyes (e.g. titanium dioxide, iron oxides, zinc oxides) that are insoluble in a medium and are applied to the skin to produce a color effect. They are used for cosmetic applications (make-up, other decorative cosmetics such as lipsticks, make-ups).

In the narrower medical language, the term pigmentation is used for a (melanotic) coloration (brown-black-brown) of skin or mucous membrane caused by melanin.

• physiological (melanotic) pigmentation = skin tanning
• pathological (melanotic) pigmentation(hyperpigmentation)

The opposite of hyperpigmentation is (pathological) depigmentation.

• Change in melanocyte count
• inadequate melanin synthesis
• Defects in the maturation, transport or transfer of melanosomes.

1. Giehl K et al (2010) Genetically caused pigmentation disorders. Dermatologist 61:567-577.