How does the sun burn skin?

While you bake in your lounge chair, ultraviolet light from the sun zaps through your skin and kills living cells that normally work to help make new skin. Ultraviolet A, UVA, can travel more deeply into the skin, but both UVA and UVB rays can burn skin.

1.为什么太阳会晒伤皮肤？

当你在躺椅里晒太阳的时候，阳光中的紫外线穿透你的皮肤，杀伤正常状态下帮助你皮肤更新的活细胞。紫外线A，也就是长波紫外线，穿透皮肤更深，不过紫外线A和B都能晒伤皮肤。

Why does sunburned skin turn red?

To repair the damage and remove the dead cells, blood vessels expand and blood flow increases to the burned parts of your body. The extra blood turns your skin red and warm.
What causes sun-kissed skin to burn and itch?

Damaged cells send messages to your brain, signaling they're injured and activating pain receptors, which makes your skin sensitive to touch

2.为什么太阳晒过的皮肤会变红？

为了修复损伤并清除死细胞，你的身体晒伤部位的血管会扩张、血流量会增大。这种多于平常的血量让你的皮肤发红发热。

Why does skin tan?

In response to the UV rays frying your inner layer of skin, your body produces more melanin pigment that darkens the skin. The pigment absorbs the radiation and protects cells from damage. Most people don't tan after just one day at the beach, or one session in the tanning bed, because it takes time to make melanin.

3.为什么被晒伤的皮肤有灼痛感并且发痒？

受损细胞向你的大脑发出信息，传递受伤的信号并激活疼痛受体，使得你的皮肤对触碰变得敏感。

Why don't redheads tan?

Melanin helps the body filter out UV radiation, but it also can be harmful. Pheomelanin, the type of melanin that makes red and blonde hair and fair skin, actually increases the risk for sun damage, such as sunburn and skin cancer.

4.为什么会晒黑？

作为对紫外线灼伤内皮层的反应，你的身体会产生更多的黑色素使皮肤颜色变深。黑色素可以吸收辐射，保护你的细胞不受损伤。不过大多数人只在沙滩上玩一天或者使用晒黑床一个周期不会晒成古铜色的皮肤，因为黑色素的合成是需要时间的。
5.为什么红头发的人不适合晒黑？（外国人以古铜色皮肤为美，这是指那些故意的人说的吧……）

How does sunscreen work?

The most effective sunscreens protect against both UVA and UVB rays. They work by either chemically absorbing UV rays or deflecting and bouncing them off your body.

6.防晒霜是怎样起作用的？

最有效的防晒霜既能防护紫外线A也能防护紫外线B。它们的工作原理要么是含有能吸收紫外线的化学物质，要么是使紫外线折射或色散，避开你的身体。

Is SPF 30 twice as good as SPF 15?

Not quite. SPF tells you how long you have before you burn. Wearing SPF 2 lets you stay in the sun twice as long as without. An SPF 30 gives you 30 times your natural protection, and deflects 9

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