What is hyperpigmentation?

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 is responsible for lighter skin tones, while eumelanin is responsible for darker skin tones.

Eumelanin acts as a sunscreen, absorbing the sun's UV rays and protecting the skin from sunburn. Studies have shown that people with high levels of eumelanin are less likely to develop skin cancers than those with low levels.

What causes skin pigmentation?

Skin pigmentation is a complex phenomenon resulting from the interaction of genetic and environmental factors.

• Genetics

Genetics play a fundamental role in determining skin pigmentation, as genes passed down from parents influence how melanocytes produce and distribute melanin in the skin.

• Sun exposure

Sun exposure is a major external factor influencing skin pigmentation. 

To protect itself from UV rays, the skin produces more melanin, resulting in a tan, which in the long term can cause changes in skin pigmentation.

• 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 can 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 can also intensify. Anyone taking medication should consult their doctor to find out if the drug could have an impact on their skin color.

What is hyperpigmentation?

Hyperpigmentation is the overproduction of melanin by the epidermis, which can lead to skin changes of all kinds.

What are the different types of hyperpigmentation?

• Age spots

Also known as liver spots or solar lentigos, these are flat, brown spots that generally appear on sun-exposed areas of the skin, such as the face, hands and décolleté.

• Pregnancy mask, also known as melasma

Melasma can be recognized by larger spots, often on the face, which can vary in color from light to dark brown.

This type of hyperpigmentation is caused by hormonal fluctuations. Progesterone and estrogen can stimulate the production of melanin, leading to theappearance of spots. Sun exposure is a major aggravating factor in melasma. Ultraviolet rays stimulate melanin production, and prolonged exposure can intensify irregular pigmentation.

There is also a racial component. Melasma is more common in darker-skinned people, particularly those of Asian, Mediterranean, Hispanic or African descent.

In addition, certain cosmetic products and the frequent use of perfumes can trigger or aggravate melasma, particularly when combined with sun exposure.

• Post-inflammatory hyperpigmentation

Post-inflammatory hyperpigmentation refers to darker patches that appear after the healing of a skin lesion, such as acne or a wound, and are the result of the healing process after skin inflammation.

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, leading to excessive melanin production in the affected area.

Melanocytes can also be activated to produce more melanin to protect the newly-forming skin. This can lead to darker pigmentation in 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 greater the chance of darker pigmentation.

• Freckles, also known as ephelides

These are flat spots, often lighter than the skin's natural color, and of genetic origin. Read our dedicated article to find out more.

• Sun spots or actinic lentigos

Actinic lentigos are flat, well-defined brown 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 referred to as sun spots, are mainly observed in people who have had significant sun exposure over the course of their lives.

• Pigmented birthmarks (nevi)

Pigmented birthmarks, also known as nevi, appear as pigmented marks on the skin, ranging from light brown to black. Recognized 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 are generally the result of genetic factors and embryonic development. These pigmented birthmarks can be present from birth or appear later in life, sometimes evolving in size and color over time. Although most neuri are harmless, some may require medical attention, particularly if they show unusual changes.

• Drug-induced hyperpigmentation

Medication-induced hyperpigmentation is excessive skin discoloration, usually brownish or grayish, caused by certain medications. This pigmentation may appear diffusely on various parts of the body, and is specific to the individual's reaction to the medication. Certain drugs, such as antibiotics or oral contraceptives, have been associated with this type of cutaneous side effect.

• Vitiligo

Vitiligo is characterized by areas of skin that lose their pigmentation, creating white or discolored patches. Recognizable by their depigmented appearance, these spots can vary in size and shape, and are often more visible on darker skin. Vitiligo results from the destruction of melanocytes, the cells responsible for melanin production, 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 are generally aimed at reducing the appearance of spots or restoring pigmentation.

 

Sources

1. Thawabteh AM, Jibreen A, Karaman D, Thawabteh A, Karaman R. Skin Pigmentation Types, Causes and Treatment-A Review. Molecules. 2023 Jun 18;28(12):4839. doi: 10.3390/molecules28124839. PMID: 37375394; PMCID: PMC10304091.
2. 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.
3. Martin A.R., Lin M., Granka J.M., Myrick J.W., Liu X., Sockell A., Atkinson E.G., Werely C.J., Möller M., Sandhu M.S., et al. An unexpectedly complex architecture for skin pigmentation in Africans. Cell. 2017;171:1340-1353. doi: 10.1016/j.cell.2017.11.015.
4. 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. Genet. 2019;57:734-744. doi: 10.1007/s10528-019-09929-x.