Skin pigmentation, which refers to the amount of melanin produced by the body, determines skin color .
There are 2 main types of melanin, both produced by melanocytes in the epidermis: pheomelanin and eumelanin. Pheomelanin gives lighter skin tones while eumelanin is responsible for darker skin tones.
Eumelanin is a sunscreen because it absorbs the sun's UV rays and protects the skin from sunburn. Studies have shown that people with high eumelanin levels are less likely to develop skin cancer than people with low levels.
What are the causes of skin pigmentation?
Skin pigmentation is a complex phenomenon resulting from the interaction between genetic and environmental factors.
- Genetic
Genetics play a fundamental role in determining skin pigmentation because genes passed down from parents influence how melanocytes produce and distribute melanin in the skin.
- Solar exposure
Sun exposure is a major external factor that influences skin pigmentation.
To protect itself from UV rays, the skin produces more melanin which causes the skin to tan and can, in the long term, cause changes in the pigmentation of the skin.
- Hormones
Hormonal changes , such as those occurring during pregnancy, can also influence skin pigmentation. A common example is the "pregnancy mask", where specific areas of the face may become darker due to hormonal fluctuations.
- Certain medications
Several medications can also lighten skin pigmentation. One class of drugs, antibiotics, can stimulate melanin synthesis, thereby increasing skin color. When certain medications, such as birth control pills, are taken together, skin pigmentation may also intensify. A person taking medication should consult their doctor to find out if the medication might impact their skin color.
What is hyperpigmentation?
Hyperpigmentation is an overproduction of melanin by the epidermis which can then cause skin changes of all kinds.
What are the different types of hyperpigmentation?
- Age spots
Also called liver spots or solar lentigos, these are flat, brown spots that typically appear on areas of the skin exposed to the sun , such as the face, hands, and décolleté.
- Mask of pregnancy, known as melasma
Melasma is recognized by larger spots, often on the face, which can vary in color from light brown to dark brown.
This type of hyperpigmentation is caused by hormonal fluctuations. Indeed, progesterone and estrogen can stimulate the production of melanin which then causes the appearance of spots . Sun exposure is a major aggravating factor of melasma. Ultraviolet rays stimulate melanin production, and prolonged exposure can intensify irregular pigmentation.
Additionally, there is a racial component. Indeed, melasma is more common in people with darker skin, particularly in those of Asian, Mediterranean, Hispanic or African origins.
Furthermore, certain cosmetic products, as well as the frequent use of perfumes, can be triggers or aggravators of melasma, particularly when associated with sun exposure.
- Post-inflammatory hyperpigmentation
Post-inflammatory hyperpigmentation is darker spots that appear after a skin lesion, such as acne or injury, has healed and are the result of the healing process after skin inflammation.
Indeed, the healing process involves a series of complex cellular events that can affect melanin production.
Cytokines, the signaling molecules released during inflammation, can stimulate melanocyte activity which leads to excessive melanin production in the affected region.
Melanocytes can also be activated to produce more melanin to protect the new forming skin. This can lead to darker pigmentation on the scarred area.
The length of time the skin is in the healing process can also influence the final pigmentation. The longer it takes to heal, the more likely you are to see dark pigmentation.
- Freckles, also called ephelides
These are flat spots, often lighter than the natural color of the skin and of genetic origin. Do not hesitate to read our dedicated article to find out more.
- Sun spots or actinic lentigos
Actinic lentigos are brown, flat, well-demarcated spots that form on the skin following prolonged exposure to the sun's ultraviolet rays. They usually appear on areas frequently exposed to the sun, such as the face, hands and décolleté, and are the result of an accumulation of sun damage over time. These spots, often called sunspots, are mainly seen in people with significant sun exposure over their lifetime.
- Pigmented birthmarks (nevus)
Pigmented birthmarks, also called nevus, appear as pigmented marks on the skin, ranging from light brown to black. Recognizable by their often round or oval appearance, these dark spots can vary in size and shape. Their location on the skin can be diverse, and they generally result from genetic factors and embryonic development. These pigmented birthmarks may be present from birth or appear later in life, sometimes changing in size and color over time. Although most nevus are harmless, some may require medical supervision, especially if they have unusual changes.
- Drug-induced hyperpigmentation
Drug-induced hyperpigmentation manifests itself as excessive discoloration of the skin, usually brownish or grayish, due to taking certain medications. This pigmentation can appear diffusely on various parts of the body and is specific to the individual reaction to medications. Certain medications, such as antibiotics or oral contraceptives, have been associated with this type of skin side effect.
- Vitiligo
Vitiligo is characterized by areas of the skin that lose pigmentation, creating white or discolored spots. Recognizable by their depigmented appearance, these spots can vary in size and shape, and they are often more visible on darker skin. Vitiligo results from a destruction of melanocytes, the cells responsible for producing melanin, although the exact cause is not fully understood. Genetic, autoimmune, and environmental factors are often associated with this skin condition. Although vitiligo is not physically harmful, it can have a psychological impact, and treatment options generally aim to fade the appearance of spots or restore pigmentation.
Sources
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- Del Bino S., Duval C., Bernerd F. Clinical and biological characterization of skin pigmentation diversity and its consequences on UV impact. Int. J. Mol. Sci. 2018;19:2668. doi:10.3390/ijms19092668.
- Martin AR, Lin M., Granka JM, Myrick JW, Liu X., Sockell A., Atkinson EG, Werely CJ, Möller M., Sandhu MS, et al. An unexpectedly complex architecture for skin pigmentation in Africans. Cell. 2017;171:1340–1353. doi: 10.1016/j.cell.2017.11.015.
- Hu S., Zhai P., Chen Y., Zhao B., Yang N., Wang M., Xiao Y., Bao G., Wu X. Morphological characterization and gene expression patterns for melanin pigmentation in Rex rabbit. Biochem. Broom. 2019;57:734–744. doi:10.1007/s10528-019-09929-x.