The deposition of coloring matter; coloration or discoloration of a part by a pigment.
Coloration of the skin as a result of the presence of a color in the tissues.
The colouring of the body, especially that produced by deposits of pigment.
Coloration of the skin, hair, and eyes with the pigment melanin. Melanin acts as a sunscreen, offering protection from the negative effects of ultraviolet light. The amount of pigment in the skin determines susceptibility to sun damage and skin cancer. Dark skin contains more pigment, which provides some protection from the sun. Pigmentation can be affected by many factors, including heredity, hormones, injury, and exposure to heat or radiation. “The result may be hyperpigmentation (an increase in pigment production) or hypopigmentation (a decrease in pigment production). Pigment changes can be temporary or permanent.
Coloration produced in the body by the deposition of one pigment, especially in excessive amounts. Pigmentation may be produced by natural pigments, such as bile pigments (as in jaundice) or melanin, or by foreign material, such as lead or arsenic in chronic poisoning.
Coloration caused by deposition of pigments.
The skin, hair, and iris of the eyes acquire their coloration from melanin, a brown or black pigment created by cells known as melanocytes. The depth of the coloration depends on the quantity of melanin present (its production is influenced by genetics and sunlight exposure). Skin can also be tinted by blood pigments, as evident in bruises.
Numerous pigmentation anomalies exist, leading to skin that is unusually light or dark, or resulting in patches of discolored skin.
Areas of pale skin develop as a manifestation of skin conditions like psoriasis, pityriasis alba, and pityriasis versicolor. These conditions prompt the shedding of skin scales, leading to a reduction in melanin content. In the case of vitiligo, segments of skin cease to produce melanin altogether.
Albinism, an uncommon genetic disorder, arises from a widespread lack of melanin, leading to notably light skin and white hair. Another hereditary condition, phenylketonuria, leads to a diminished melanin level, causing individuals affected by the condition to possess fairer skin and hair than the rest of their family members.
Transient occurrences of darkened skin regions can emerge as a result of conditions like eczema or psoriasis, pityriasis versicolor, or chloasma (the emergence of dark facial patches due to hormonal shifts). These patches of heightened pigmentation can also manifest after the application of fragrances and cosmetics containing chemicals that induce photosensitivity.
Irreversible regions of intense pigmentation, like freckles, moles, or specific types of naevi, typically arise from irregularities within certain melanocytes. Acanthosis nigricans, a condition that could stem from either hereditary factors or external causes, is identified by the presence of velvety, thickened dark patches on the skin. Skin darkening unrelated to sun exposure can manifest in certain hormonal disorders like Addison’s disease and Cushing’s syndrome.
Certain instances of unusual discoloration stem from elevated levels of specific pigments or other substances within the bloodstream. An abundance of the bile pigment bilirubin during jaundice leads to a yellowing of the skin, while an excessive iron content in the blood due to haemochromatosis results in a bronze hue. Abnormal accumulation of blood vessels, as seen in haemangioma, can also cause skin discoloration. Furthermore, temporary skin discoloration can arise from bruises, where leaked blood from ruptured vessels accumulates beneath the skin.
The deposition of pigment; the process of adding color or causing discoloration through the presence of pigment.