Melanin pigment is the natural polymeric molecule that imparts colour to our skin. It is a granular pigment produced by specialized cells called melanocytes. Its production involves a complex biochemical process. It starts with phenylalanine amino acid converted to melanin via a series of intermediate steps. The reaction is catalyzed by the tyrosinase enzyme and this enzyme is vital for the whole chemical transformation. The whole process is termed “Melanogenesis”.
Besides its colouring nature, melanin has a vital role in skincare science. It absorbs ultraviolet radiation of the solar spectrum and dissipates it back into the air. It also can capture free radicals formed on skin exposure to solar radiation. This is how melanin protects DNA degradation and ensures our healthy skin life. Interestingly, people living at the equator mostly have dark skin colour while the population living in countries far away from the equator line are mostly light skinned in tone. This is due to the “Natural Protection Mechanism” where a human biological system produces more melanin in areas where solar radiations are strong to protect skin quality. However, at the same time, a European person living in Africa would still have a light skin tone. Why is it so? This is due to genetic programming controlling melanin production.
There are two types of melanin;
- Pheomelanin
- Eumelanin.
Pheomelanin is red yellow-coloured while eumelanin is the brown-black shade. The tone of skin colour depends upon the concentration of melanin and its type.
Skin pigmentation may suffer some problems. In dermatology, these problems are addressed and clinical science offers remedies for them. There are two possibilities of having pigmentation disorder
- Hypopigmentation (Decreased melanin level)
- Hyperpigmentation (Increased melanin level)
Let’s analyze more of both in more details
Hypopigmentation
The skin might develop some light-coloured patches or spots due to low levels of melanin present there. These spots have a relatively lighter colour tone compared to the rest of the body. These spots are easily observable. There could be different mechanisms involved here. The basic reason is either low melanin production in that particular localized area or melanin present has been degraded. Scientific studies have reported various types of such cases and reasons leading to this problem.
Albinism
Albinism is probably the most prevalent skin pigment disorder among the population. It could happen even in infants and kids. It is a genetic disorder in which almost the whole body including hair, eyebrows, and other facial skin can have depigmentation. Skin tone may be significantly lighter compared to their parents and other family members. It is due to decreased melanin production as a result of genetic coding. The patient is advised to avoid sun exposure, use cotton clothes with opaque colour shades, and use sunscreen products for protection. High exposure to solar light may cause severe red scars and even sunburns.
Vitiligo
Vitiligo stands for pinkish skin tone. It is due to a complete lack of melanocyte activity. It is believed that melanocytes undergo a self-destruction mechanism due to the accumulation of toxic substances in the cell which leads to cell death. Therefore there is not melanin production in that particular body area.
Here again, the patient is advised to avoid sun exposure. A dermatologist can prescribe a high dosage of sunscreen formulations.
Post-Inflammatory Depigmentation
Prolonged disease or sickness requires continuous medication. This puts our immune system under extreme stress and can cause several health problems. In certain cases, it may follow skin issues such as eczema, psoriasis, and uneven pigmentation. In general, the more severe the inflammation, the more likely pigment is to decrease in its wake. These problems are most significant in darker-skinned individuals. However, the skin usually re-pigments with time. Exposure to the sun makes the patches more obvious.
Hyperpigmentation
Hyperpigmentation is opposite to hypopigmentation where we have higher melanin content localized in certain parts of the body. The skin tone gets darkened and these patches may grow. Interestingly, hyperpigmentation is relatively more common than hypopigmentation. There are various forms of this issue such as
Freckles
Freckles are small black-brown spots mostly observed in facial areas. They are more visible in fair complexion skin and get worst with sun exposure. The fact is, they have the same number of melanocyte cells, and however, due abnormal to biochemical activity, they over-produce melanin. This is programmed genetically. They appear as a cluster of cells with high melanin concentration. Ultraviolet radiations-B (UV-B) induce darkening of these freckles.
The remedy to freckle is having minimum sun exposure, especially during summer times. Cosmetics formulations having organic or inorganic sunscreen can protect against ultraviolet radiation and help in controlling their intensity. Skin lightening formulations containing kojic acid or exfoliation using alpha-hydroxy acids can also improve the skin tone.
Lentigo
Lentigo is light to dark brown macules ranging from 1 mm to 1 cm in size. They appear generally in childhood as a few scattered lesions and often on areas not exposed to 0020 -jythe sun, even around the mucous membranes. Just like other cases, exposure to solar radiation may increase their intensity and they are common after middle age on the backs of the hands. In contrast to freckles, lentigines have increased numbers of melanocytes leading to higher melanin production.
Treatment is usually prevention. Patients better avoid exposure to the sun and the use of sunscreens is the best approach. Cryotherapy offers good results but care must be taken to not cause hypopigmentation. Melanin specific high energy lasers and intense pulsed light are also effective. Topical therapies are also effective for lightening lentigines such as daily application of tretinoin combined with a retinoid and alpha hydroxy acid.
Melasma
Melasma is probably the most studied cases in recent times because of its severity and magnitude. It is acquired hyperpigmentation occurring on sun-exposed skin, especially the face. The areas of increased pigmentation are well defined and the condition is much more common in women. It generally affects all ethnic groups but is most prevalent in dark-skinned individuals. The factors that can make the situation worst are sunlight, pregnancy (‘the mask of pregnancy, and oral contraceptives. Most of the extra melanin lies in the epidermis, but there is some in the dermis too, making treatment difficult. In severe cases, melasma may lead to cancer because of localized inflammation and cell death.
Melasma is challenging to treat because of the presence of melanin at varying depths in the dermis and epidermis. Even minor sun exposure can reactivate the process. So, the treatment regimen must include sun avoidance using broad-spectrum sunscreen and hats. Skin lightening agents are helpful. Topical lightening agents employed include tyrosinase inhibitors such as alpha arbutin, kojic acid and azelaic acid.
Chemicals causing hyperpigmentation
Any severe disease, such as malabsorption, AIDS, tuberculosis, or cancer, maybe induce hyperpigmentation. Certain drugs are photosensitizing and can cause hyperpigmentation. For example, Busulfan and bleomycin used to treat some forms of leukaemia, however, they may cause hyperpigmentation.
Summary
Pigmentation disorders are common and involve complex biological processes. Advancement in dermatological science has made a significant achievement to address this problem. Topical formulations containing various chemical agents can improve the situation. Laser treatment is popular among patients as they provide relief relatively quickly. One factor common and important is “Sun”. Avoid sun exposure as ultraviolet radiation may make it worst. Regular application of sunscreen is a must.
Bibliography & Further reading
1. Weller, R. B.; Hunter, H. J. A.; Mann, M. W., Clinical Dermatology. Wiley: 2015.
2. Burgess, C. M., Cosmetic Dermatology. Springer Berlin Heidelberg: 2005.
3. Dayan, N., Skin Aging Handbook: An Integrated Approach to Biochemistry and Product Development. William Andrew: 2008.
4. SHAI, A., Handbook of cosmetic skin care. 2015.