Everyone is born with a color of skin. Orientals born with yellowish skin have never stopped on the road of "whitening".
How white can you be? What determines a person's skin color change? Life Times interviewed a dermatologist to answer your questions.
Interviewed experts
Yang Xichuan, Professor of Dermatology, Southwest Hospital of Army Military Medical University
Zhang Xiaofeng, attending physician of dermatology, Plastic Surgery Hospital, China Academy of Medical Sciences
The skin color on the inner thigh is the whitening limit.
Skin color and skin quality are determined by genes, but they are also influenced by acquired external factors. How to judge how white a person's skin can be?
Roll up your sleeves or trouser legs and look at your inner thighs and arms. The skin color of these two parts is basically the limit of your whitening (without medical beauty and cosmetics).
These parts are less affected by ultraviolet rays and are closest to people's natural skin color.
Why is the skin divided into so many "color numbers"
White skin, pink skin, yellow skin, yellow-white, yellow-white ... obviously all skin, why are they divided into such multi-color numbers?
People's skin color is mainly influenced by two kinds of melanin: dark brown true melanin and red yellow brown melanin.
There is no difference in the total number of melanocytes in human body, but because of the different number, size and aggregation degree of melanosome in melanocytes and keratinocytes, different skin colors appear.
In addition to skin color, the difference in the ratio of the two melanin will also affect the color of hair and eyes.
Quickly judge skin color
A simple method can quickly judge your skin color-vascular method. Observe the color of the medial wrist vein under natural light;
Ultraviolet rays: tanning and aging at the same time.
Ultraviolet light is the biggest resistance on the road to whitening. Among the factors of skin aging, natural aging only accounts for about 20%, and the rest are caused by photoaging.
Ultraviolet light is the chief culprit of photoaging, which can be divided into UVC (short wave), UVB (medium wave) and UVA (long wave).
Short-wave ultraviolet rays will be intercepted by the ozone layer when they hit the earth, so the UVC reaching the surface of the earth is close to zero, and UVA and UVB are the main damages to the skin.
UVB can cause spots on the skin.
After intense sunlight, the skin will sting and turn red, which is the immediate response of skin defense against UVB.
If the damage of UVB to epidermal cells persists, it may activate melanocytes and promote the formation of melanin spots.
Sunburn is an inflammatory reaction. If it is not repaired in time, acute inflammation will turn into chronic injury, and some people will have pigmentation, which will lead to black skin.
UVA can wrinkle the skin.
UVA is called the "tanning section" of ultraviolet rays, which darkens the skin and leads to skin aging.
The dermis reached by UVA contains collagen and elastin. Long-term exposure to UVA will destroy its structure and make the skin foundation "collapse" and wrinkle.
In addition, the use of hormone ointment, acne drugs and other drugs may also lead to pigmentation and dark skin color.
Scientific sun protection and ultraviolet protection
Sunscreen is not only for whitening, but also a key element of basic skin care.
Physical sun protection
The season with the highest ultraviolet intensity is late spring and early summer, especially from 10 in the morning to 16 in the afternoon. Pay attention to sun protection, try to wear a hat and trousers when going out to protect your skin.
Chemical sun protection
In order to evaluate the effect of sunscreen, two indicators-SPF and PFA(PA) have been formulated internationally.
SPF: the ability to prevent UVB, that is, the time to protect the skin. The higher the index, the stronger the protection ability.
PA: the ability to prevent UVA, that is, the ratio of tanning time when using sunscreen to tanning time when not using sunscreen. The more "+"after PA, the better the sunscreen effect.
In the morning and evening of summer and rainy days, you can choose products with low SPF value;
Under the medium-intensity sunlight, choose the products of SPF8~ 15, PA+ or PA++;
In summer, under strong outdoor sunlight, products with SPF above 25 and PA+++ should be selected.
Studies have shown that extreme sun protection may affect the synthesis of vitamin D.
However, our daily sun protection is not so strict. Unless we wrap every inch of skin and completely block ultraviolet rays for a long time, it will not cause insufficient vitamin D synthesis.
Scientific sun protection will not lack calcium, and there is no need to bask in the sun "without shelter" in order to promote the production of vitamin D and the absorption of calcium.