Since black skin has its own characteristics, it is essential to know how it works to take care of it properly. Knowing your skin from the inside is crucial to make the right cosmetic choices.
From a structural standpoint, black skins are similar to Caucasian skins, except for a few details.
They are obviously also a protective organ, but if they are not thicker, they are denser: this can be seen with their stratum corneum, which is composed of 12 layers, while that of a Caucasian individual only has eight. The dermis is more solid and compact.
Dark skins naturally receive more sun, i.e. infrared rays, so they are structured in such a way that that they lose less water. This function is clearly visible inside the dermis: the cells are more joined. Moreover, the stratum corneum is richer in lipids and produces more hydrolipidic film, an additional protection against water evaporation.
On top of that, sweat glands – responsible for perspiration – are a bit bigger and more numerous: black skins are adapted to absorb more infrared rays, and the heat of their environment requires more efficient thermoregulation – perspiration should be more abundant. Their black colour also amplifies the infrared absorption phenomenon.
When they are exposed to the sun, Caucasian skin melanocytes produce melanin, which is responsible for skin colouration: keratinocytes catch UV rays and pass on a message to melanocytes to obtain a sort of ‘molecular beach umbrella' to protect themselves.
In addition to this identical mechanism, dark skins' melanocytes work even when there is no light. Melanin grains are bigger, more stable, and egg-shaped. Melanocytes are programmed to produce melanin on a constant basis.
Sometimes, cells do not work properly: that is when pigment spots, or even vitiligo – depigmentation on large skin areas – appear.
These multi-factorial phenomena can be explained by gene mutations in the cells at stake. As a result, either melanocytes no longer produce melanin, or melanin is no longer transmitted to keratinocytes.
From a structural standpoint, black skins get tanned and react the same way as clear skins. It should be known that keratinocytes seek the help of melanocytes to protect the dermis. It is necessary to use sunscreen products for long exposures. Although these epidermises are less subject to sunburns, they are not fully protected against the damages of UVAs, which penetrate the skin in depth and are responsible for melanomas (skin cancer).
And yet, the sun is essential: to make vitamin D, which guarantees the balance of the skin and microbial environment, the solidity of our bones, as well as our good mood, black epidermises need six times more UV rays than white skins.
Phototype 4/5 dark epidermises need UVBs to guarantee their balance. That is the reason why they suffer from dryness, or even atopy, when they live in temperate environments, where luminosity is weaker.
Skin dryness may be explained by a rupture between the genome and the exposome, which is no longer the reference. The skin is not ‘adapted' yet.
To best curb this phenomenon, the cosmetics answer should be qualitative. Choose products enriched in vitamin D, with a base of moisturizing, anti-dehydration molecules, and ceramides to make the epidermis more comfortable.
A few little pimples
In parallel to skin dryness, sebaceous glands are bigger and produce more sebum. Combined with more perspiration, the formation of the hydrolipidic film is more important to provide better protection against UV rays. The problem is, this hyperseborrhoea is the ideal ground for the development of the bacteria responsible for the appearance of small pimples. All black-skinned individuals do not and will not experience acne, it is just that their microbial environment is more favourable to its appearance.
We often notice that dark skins are less quickly marked by signs of aging. As a result, the skin's biological age seems lower than the chronological age. This can be explained by several factors.
• First, oxidative stress, which is triggered by the exposure to UV rays, is 90% responsible for aging.
• Black epidermises are less impacted by UV penetration, since they are better protected on the surface. UVs are slowed down and create less inflammation.
• Then, fibroblasts, the cells that produce the hyaluronic acid/collagen/elastin complex, are bigger and more efficient than those in Caucasian skins. The skin is programmed to remain elastic and firm.
• Lastly, the exposome also plays a direct role. When these individuals live in low-lit areas, their skins do not need to defend themselves against UV aggressions, and they age less fast.
If fibroblasts are very efficient and work faster, it creates a problem when the skin heals. Collagen overproduction results in the appearance of a thick skin layer in the wound area. That is called keloids. However, these scars are not hazardous for health.
For further information
• See the article: How to take good care of black skins: what are the right actives? The right products? The right rituals?
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