We often hear about Melasma, Chloasma, hormonal spots, sun spots, photoaging. But we do not distinguish well what each concept is, neither what they appear, nor their treatment.
All of these conditions are different types of hyperchromia or commonly known as skin pigmentation.
Hyperchromia (pigmentation) and melanin of the skin
Skin pigmentation is caused by the combination of four pigments located in the dermis and epidermis: Oxygenated hemoglobin, deoxygenated hemoglobin, carotene deposits, as well as in other exogenous pigments (medicines, metals, etc.) and epidermal melanin (which gives ethnic pigmentary differences).
Melanin is a complex chemical structure biopolymers and it’s the main pigment responsible for the normal color of the skin and hair.
It is found in all individuals forming complex combinations that give rise to the multiple shades of skin color. It is regulated by genetic, environmental, and endocrine factors, which modulate the amount, type, and distribution of melanin in the skin, hair, and eyes.
There are two types of melanin:
• Eumelanin: Blackish brown pigment that provides dark colorations
• Pheo-melanin: Yellowish or brownish-red pigments that make up a higher proportion of sulfur than the above and they are responsible for clear colorations.
Synthesis of melanin and its protective function:
MC1R receptors regulate skin pigmentation, UV responses and the risk of melanoma. Its activation increases the production of melanin and its deposition in the epidermis, limiting the penetration of UV rays into the skin.
The synthesis of melanin takes place inside melanosomes, from tyrosine. A succession of tyrosine oxidations catalysed by tyrosinase, leads to the synthesis of DOPA (dihydroxyphenylalanine) to produce then a common intermediate compound: dopaquinone. From this point, two distinct pathways lead to the formation of eumelanins and pheo-melanins.
The production of pheomelanin depends on the incorporation of a cysteine and the retention of sulfur after the synthesis of dopaquinone.
Tanning is an adaptive pigmentation and is a mechanism for protecting the skin against solar aggression (the MC1R receptors are activated). The more pigmented the skin, the more it is protected against negative effects such as photo aging and skin cancer.
The melanin barrier is the most effective device against solar radiation, in which the ultraviolet light spectrum is the area that affects the skin.
Ultraviolet rays are subdivided into 3 types:
(thanks to the oxidation of melanin present in melanocytes)
(tanning), thickening of the stratum corneum, solar erythema.
|UVC||Retained by the Atmospheric Ozone Layer
Hyperchromia or Hyperpigmentation:
We can find many types of hyperpigmentation, which are classified according to their ethology:
Hyperchromia caused by melanocytic hyperactivity or proliferation:
|Ephelides (Freckles)||• There is an increase in melanin pigment in the epidermis
• Are small in size and located in sun-exposed outdoor areas
• Appears from childhood and has hereditary character
|Lentigo||• They are brown or brownish-blackish spots, isolated or grouped
• Can be located in any area of body surface
• There is an increase in melanocytes of the epidermis and they are induced by the overexposure of the sun, in particular, the senile lentigo appear in people of 50 years that has been exposed repeatedly under the sun without the proper protection
|Melasma or Chloasma
|• Light brown or dark brown spots, which develop slowly and systematically
• Predominantly in female and it has been associated with hormonal factors, cosmetics, sun exposure and family trend
• Common during pregnancy
|Nevus (Moles)||• Blackish hyperpigmentation, which may also have hair
• Congenital abnormality that can also be acquired
• If there are signs of oozing, itching, pain, or inflammation, it is advisable to consult your doctor.
Hyperchromia due to photosensitisation:
On the other hand, hyperchromias can be caused by photosensitization of solar radiation in contact with chemical agents such as perfumes, plants containing furocumarin with photosensitive properties, facial powders with alamine that can give photodermatosis. And as we have already commented, certain medicines with photosensitising properties such as psoralens or diphenhydramine, etc.
Cold, heat and mechanical rubbing, applied repeatedly, are also agents that can cause an increase in skin pigmentation
Post inflammatory hyperchromia (BPH):
In skin disorders such as acne, eczema, herpes, burns, among others. A process of inflammation of the skin is typical of these conditions, which, as a consequence, after this inflammatory process can lead to hyperpigmentation.
How can radiation affect our skin? SKIN PHOTOAGING
The sun is a good ally for capturing Vit D, to have a beautiful skin tone and makes us feel better mentally. But it is one of the main factors of premature aging.
Photoaging is an acceleration of the natural intrinsic aging of the skin induced by the damage caused by ultraviolet radiation from the sun. It is characterized by the appearance of wrinkles, roughness, laxity and unequal pigmentation of the skin. And it can take decades to manifest.
In the short term, when there is excessive exposure of ultraviolet radiation, it can produce an augmentation of pigmentation or melanogenesis, inflammation and erythema caused by sunburn. After exposure of ultraviolet rays, the skin undergoes histopathological changes. Among them a thickening of the epidermis, especially of the stratum corneum, and to the dermis. This thickening causes a higher production of keratinocytes, and at the same time an increase in the biosynthesis of DNA, RNA and proteins, and as a consequence there is a greater degradation of these.
Epidermal DNA is highly susceptible to structural modification by solar UV radiation even in exposures that do not produce erythema. If the damaged DNA is not repaired, it can result in characteristic mutations that lead to skin mutations and later to the possibility of skin cancer. The sun’s UV rays also cause a degradation of the main components that give stiffness, turgidity and elasticity to the skin such as collagen and elastin, and an inhibition of their synthesis. This impairs the structural integrity of the skin during photoaging, causing wrinkles and other signs of age.
It also produces an immunosuppression, where the Langerhans cells (in charge of the defense) are exhausted in contact with UV rays, therefore the skin is more exposed to external aggressions.
Two of the main methods to lighten the color of the skin by reducing skin pigmentation are: bleaching the melanin already formed, and preventing the formation of new melanin.
The results of the discoloration of the skin spots are visible after long periods of treatment and, above all , if appropriate photoprotection precautions are taken.
Depigmenting substances slow or retard this process of melanogenesis or melanin formation by several pathways or stages.
- Destruction of melanocytes (Rucinol (4-n-butyl resorcinol, N-acetyl-4-S- cysteaminophenol)
- Inhibition of formation and alteration of melanosome structure (lipyl acid, ellagic acid)
- Inhibition of the biosynthesis of tyrosinase: blocking of the factors that induce its synthesis or its enzymatic activity (lactic acid and placental extracts), inhibition of its enzymatic activity (as in the case of plant extracts), formation of a substrate that inhibits the activity of tyrosinase activity and inhibition of glycosylation (some amino sugars such as glucosamine or galactosamine).
- Inhibition in the formation of melanin, by a reduction of the dopamine reaction to dopa. ( Vit C , reduced glycation and cysteine , albatin )
- Interference with melanosome transfer ( Tetrinoine
- Increased degradation of melanosomes in keratinocytes. (glycolic acid, phenol, paraaminobenzoic acid and paraphenylenediamine)
- Stimulation of cellular activity (Vit c, albatin )
- Discoloration of the formed melanin. (AHA, BHA)
- https://idus.us.es/bitstream/handle/11441/66485/G%F3mez%20Gonz%E1lez,%20Mercedes.pdf;jsessionid=48C93DD94C4310B2430D85C1B1B15900?sequence=1&isAllowe=y https://www.elsevier.es/es-revista-offarm-4-articulo-sustancias-despigmentantes-metodos-aclaramiento-del-13038004