Have you found that the pursuit of "white" by oriental women is endless? And those who are already white want to be whiter? Happily, with the development of science and technology, whitening products are more and more diversified, and the ways of whitening are also more and more. But before whitening, have you ever known how the skin turns black? Why does it turn black? Of course, it's not just suntanning.
It's related to blackening.
We know that skin blackening is a manifestation of melanin deposition. Melanin is a protein derivative, brown or black, produced by melanocytes. Melanocytes are with many antennae extending simultaneously to dozens of "keratinocytes" in the surrounding epidermis. Once the melanin is secreted, the antennae are used to send it to the cuticle. Then, melanin slowly moves to the skin surface along with epidermal cells, and also falls off with metabolism. The root cause of skin blackening is the increase of melanin content in epidermis for various reasons. There are many factors affecting the formation of melanin, which can be generally divided into endogenous factors and exogenous factors.
Melanocytes have estrogen receptors, so they are more sensitive to estrogen, which can accelerate the production of melanin. During pregnancy, especially in the second trimester of pregnancy, estrogen, progesterone and melatonin levels will rise, so there are often some spots. Staying up late can also affect hormone secretion in the body, leading to melanin production and dark complexion.
2. Skin inflammation
Acne, contact dermatitis can cause the deposition of pigments. The reason is that leukotrienes and thromboxane produced during inflammation can stimulate melanocytes to produce more melanin. It also causes morphological changes of melanocytes, which is more conducive to the transfer of melanosomes to surrounding keratinocytes.
Diseases that can change normal skin color or even darken, the most common of which are endocrine system diseases, chronic consumptive diseases, malnutrition diseases and so on. These diseases can make the skin brown or dark brown and distribute in exposed areas such as face, back of hand, joints or under pressure and friction. Again, chronic liver disease can cause facial chloasma or periorbital darkening. In addition, melanin in patients with melanosis mostly accumulates in the face, especially in the forehead, cheeks, behind ears and neck, which is very obvious.
Most people know that blackening is related to sun exposure. Ultraviolet (UV) light in the sun is the culprit, and is the main physiological stimulation of human melanocyte proliferation and skin pigmentation. Skin blackening is mainly caused by medium and long-wave ultraviolet (UVB and UVA). Ultraviolet radiation can stimulate the rapid activation of melanocytes in the skin base, shuttle through the epidermal cells, and then transfer melanin protein through the cell metabolic layer to keratinocytes. The more melanin protein is transferred to keratinocytes, the darker the skin color will be. After 2-3 days of activity and sediment metabolism, the skin changes from white to red and from red to black.
2. Drugs and chemicals
Some drugs and chemicals can also cause skin pigmentation.
Drugs: some antibiotics (sulfonamides and tetracyclines), diuretics, non-steroidal anti-inflammatory drugs, analgesics and some psychotropic drugs. If you take oral contraceptives for a long time, your cheeks, forehead and nose will also get spots.
Chemicals: cyclophosphamide, 5-fluorouracil, doxorubicin, daunorubicin and bleomycin. The mechanism of action is still unclear, which may involve direct toxicity, stimulation of melanocytes and inflammation.
Food rich in copper, iron, zinc and other metal elements is also the cause of skin blackening. These metal elements can directly or indirectly increase the amount and activity of tyrosine, tyrosinase and other substances related to melanin production. These foods mainly include animal liver, kidney, oyster, shrimp, crab, beans, walnuts, black sesame, raisins and so on.
These are the culprits of skin darkening. Skin darkening is not caused by pure ultraviolet radiation. It is affected by multiple factors. For ultraviolet radiation, disease and other exogenous factors, what we can do is to prevent and avoid. For hormones and other endogenous factors, we can adjust our lifestyle to improve. Having said so much, I hope it will be helpful to your whitening cause, and more comprehensive whitening countermeasures and methods will be introduced in detail later. Please look forward to it.