Hyperpigmentation can be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris.[1][2][3]: 854 People with darker skin tones are more prone to hyperpigmentation, especially with excess sun exposure.[4]
Many forms of hyperpigmentation are caused by an excess production of melanin.[4] Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by melanocytes at the lower layer of the epidermis. Melanin is a class of pigment responsible for producing color in the body in places such as the eyes, skin, and hair. The process of melanin synthesis (melanogenesis) starts with the oxidation of l-tyrosine to l-dopa by the enzyme tyrosine hydroxylase, then to l-dopaquinone and dopachrome, which forms melanin.[5]
As the body ages, melanocyte distribution becomes less diffuse and its regulation less controlled by the body. UV light stimulates melanocyte activity, and where concentration of the cells is greater, hyperpigmentation occurs. Another form of hyperpigmentation is post-inflammatory hyperpigmentation. These are dark and discoloured spots that appear on the skin following acne that has healed.[6]
Melasma, also known as 'chloasma' or the “mask of pregnancy,” when it occurs in pregnant women.— It is a common skin problem that causes dark discolored patchy hyperpigmentation. It typically occurs on the face and is symmetrical, with matching marks on both sides of the face. The condition is much more common in women than men, though men can get it too. According to the American Academy of Dermatology, 90 percent of people who develop melasma are women.[7]
There are a wide range of depigmenting treatments used for hyperpigmentation conditions, and responses to most are variable.[11]
Most often treatment of hyperpigmentation caused by melanin overproduction (such as melasma, acne scarring, liver spots) includes the use of topical depigmenting agents, which vary in their efficacy and safety, as well as in prescription rules.[12]
Many topical treatments disrupt the synthesis of melanin by inhibiting the enzyme tyrosine hydroxylase.[5]
Several are prescription only in the US, especially in high doses, such as hydroquinone, azelaic acid,[13] and kojic acid.[14] Some are available without prescription, such as niacinamide,[15][16]l-ascorbic acid,[citation needed] retinoids such as tretinoin,[17]orcysteamine hydrochloride.[18][19] Hydroquinone was the most commonly prescribed hyperpigmentation treatment before the long-term safety concerns were raised,[20] and the use of it became more regulated in several countries and discouraged in general by WHO.[21] For the US, only 2% is at present sold over-the-counter, and 4% needs prescription. In the EU hydroquinone was banned from cosmetic applications.[22]
Oral medication with procyanidin plus vitamins A, C, and E also shows promise as safe and effective for epidermal melasma. In an 8-week randomized, double-blind, placebo-controlled trial in 56 Filipino women, treatment was associated with significant improvements in the left and right malar regions, and was safe and well tolerated.[23] Other treatments that do not involve topical agents are also available, including fraction lasers[24] and dermabrasion.[12]
Laser toning using YAG lasers[25] and intense pulsed light have been used to treat hyperpigmentation such as melasma and post-inflammatory hyperpigmentation.[26]
^Gupta, AK; Gover, MD; Nouri, K; Taylor, S (December 2006). "The treatment of melasma: a review of clinical trials". Journal of the American Academy of Dermatology. 55 (6): 1048–65. doi:10.1016/j.jaad.2006.02.009. PMID17097400.
^Mansouri, P.; Farshi, S.; Hashemi, Z.; Kasraee, B. (2015-07-01). "Evaluation of the efficacy of cysteamine 5% cream in the treatment of epidermal melasma: a randomized double-blind placebo-controlled trial". The British Journal of Dermatology. 173 (1): 209–217. doi:10.1111/bjd.13424. ISSN1365-2133. PMID25251767. S2CID21618233.
^Hyrdoquinone Guidance published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization. World Health Organization. 1994. hdl:10665/39218. ISBN9789241571579.
^Kim, Young Jae; Suh, Hyun Yi; Choi, Myoung Eun; Jung, Chang Jin; Chang, Sung Eun (2020-04-17). "Clinical improvement of photoaging-associated facial hyperpigmentation in Korean skin with a picosecond 1064-nm neodymium-doped yttrium aluminum garnet laser". Lasers in Medical Science. 35 (7). Springer Science and Business Media LLC: 1599–1606. doi:10.1007/s10103-020-03008-z. ISSN0268-8921. PMID32300974. S2CID215794622.
