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How Does Moisturizer Work
保湿霜是怎样发挥作用的
It’s the dead of winter. And… well, you know what that means: curling up with some hot cocoa,watching friends on Netflix and staring at your dry, cracked skin.
又要到数九寒冬了。你知道这意味着什么：蜷缩在被子里，端着一杯热可可，浏览朋友圈，以及盯着自己干燥皴裂的皮肤头疼。
Wait, what? When temperatures drop and heaters kick on, indoor air gets drier.
等等，你说什么？当气温下降，打开暖气的时候，室内空气会变得更加干燥。
That sends many of us scrambling for a moisturizer to ease the unsightly and irritating effects of dry skin.But what do these products actually do?
这让我们许多人拿起保湿霜，缓解干燥皮肤的不适和刺激。但是这些保湿产品是怎样发挥作用的呢？
As the name suggests, their job is to make your skin more moist. Skin dries out by a normal process with a fancy scientific name: transepidermal water loss.
就像它的名字，保湿霜的作用就是让你的皮肤更加湿润。皮肤正常的干燥过程有一个科学术语描述：经表皮水份丢失。
Or, if you like funny-sounding abbreviations, tewl.
或者，如果你喜欢发音风趣的缩写tewl。
Blood vessels only supply moisture to the middle layer of skin, the dermis.From there, water moves outward through to the epidermis before it evaporates.
血管只为皮肤的中间层——真皮保湿。水分从真皮向外渗透到表皮，然后蒸发。
A moisturizer’s job is to trap or replenish the moisture in the epidermal layer.
保湿霜的作用就是将水分锁在皮肤表层。
Moisturizers come in three varieties: occlusives, emollients and humectants.Most products you buy have a combination of some or all of these.
保湿霜共有三种：闭塞剂，润肤剂和保湿剂。你购买的大部分保湿霜都含有其中两种或三种成分。
Occlusives are the old school moisturizers,and they work in the simplest way possible.
闭塞剂是旧式保湿霜，以最简单的方法发挥作用。
They form a barrier over the skin that water can’t penetrate, stopping evaporation and keeping your skin moist.
它们在皮肤上形成一层水不能穿过的壁垒，防止水分蒸发，保湿皮肤湿润。
The best in the biz is petroleum jelly, sold as vaseline.It cuts tewl by 98 percent.The long carbon chains of the molecules that make up occlusives repulse water.
其中最有效的产品或许是凡士林。可以减少98%的水分流失。闭塞剂分子中的长碳链不亲水。
The only problem? You don’t really want to walk around covered in vaseline.
唯一的问题？你不想涂着凡士林走来走去。
More popular these days are the emollients.
现在流行的大部分保湿霜是润肤剂。
Instead of coating the skin, these are designed to penetrate, making skin feel softer and more flexible.
润肤剂不是在皮肤表层形成一层保护膜，而是通过渗透让皮肤更柔软，更有弹性。
They are made from similar chemicals as occlusives: molecules with long fatty carbon chains like stearates and castor oil.
它们是用类似闭塞剂的化学物质制成的：有着长长的脂肪碳链的分子，就像硬脂酸盐和蓖麻油一样。
But they work differently.The outermost layer of your skin has a‘brick-and-mortar’ structure where the bricks are dead cells, called corneocytes, and the mortar is made of fatty layers of lipids. Corneocytes are linked by proteins that form a strong barrier between your body and the bacteria,microbes and toxins in the outside world.
但是它们的作用方式不同。皮肤的外层有一个“砖瓦加水泥”的结构，其中砖瓦就是死细胞，叫做角化细胞。水泥是由多层脂质组成的。角化细胞由蛋白质连接起来，在身体和外界的细菌，微生物以及毒素之间形成一层壁垒。
The ‘brick-and-mortar’ stacks are thicker in places like your palms, but thinner on softer skin like your face.
“砖瓦加水泥”结构在手掌等地方更厚，在膝盖等柔软的皮肤部位更薄。
When the moisture level in the air goes down,the protein links break apart and fractures develop between groups of corneocytes.
当空气湿度下降的时候，蛋白质链接就会破裂，角化细胞之间就会出现皴裂。
Emollients get beneath the skin’s surface and fill in these gaps, keeping tewl under control and helping your skin feel smooth.
润肤剂渗透到皮肤表层一下，填补这些空缺，控制皮肤失水，让皮肤感觉光滑。
The third kind of moisturizers are humectants.
第三种保湿霜是保湿剂。
Broadly, these molecules help attract and retain moisture in the epidermis.
概括地说，这些分子帮助表皮吸收和保持水分。
Humectants help get the younger, moist cells towards the outer layer of skin, as well as reduce the flakiness of dry skin.
保湿剂可以让更年轻，更湿润的细胞到达皮肤外层，并减少干燥皮肤的成片脱落。
Humectants also stimulate the body’s natural production of ceramides,waxy molecules that reduce tewl.
保湿剂还可以刺激皮肤自然生成磷脂质，可以减少皮肤水分流失的蜡质分子。
So don’t leave your skin out to dry this winter.Grab some lotion and stay hydrated.Your corneocytes will thank you.
所以，这个冬季不要让你的皮肤失水了。涂抹一些润肤露来保湿。你的角化细胞会感谢你的。
