Whats sweat?什么是汗水？Your body works best when its temperature is about 37? Celsius. When your body gets hotter than that, your brain doesnt like it it wants your body to stay cool. So the part of your brain that controls temperature, called the hypothalamus, sends a message to your body, telling it to sweat.人体体温在37摄氏度时，身体各功能活动最佳。当体温多达这个温度时，大脑就不乐意了，它要让体温降下来。

所以大脑中掌控体温的部分下丘脑就不会收到一个信号给身体，告诉他它要排汗。Then special glands in your skin called sweat glands start making sweat. Sweat is also known as perspiration, and it is made almost completely of water, with tiny amounts of other chemicals like ammonia, urea, salts, and sugar.人体皮肤中有种尤其的腺体叫汗腺，负责管理黏液汗液。汗液完全仅有是由水构成，也所含微量的化学元素，还包括氨、尿素、盐和糖。The sweat leaves your skin through tiny holes called pores. When the sweat hits the air, the air makes it evaporate. As the sweat evaporates off your skin, you cool down.汗液通过皮肤上的小孔即毛孔废气出来。

当汗液和空气认识之后，就不会冷却。汗水一旦冷却，人体的体温就不会降下来。Sweat is a great cooling system, but if youre sweating a lot on a hot day, you could be losing too much water. Then you need to put liquid back in your body by drinking plenty of water so you wont get dehydrated.呕吐是很好的降温系统。

但是，如果你在天冷的时候出有了很多汗，你就有可能萎缩过多的水分。这时，你就必须通过大量睡觉来补足体内水分，不然你就不会水解。Why does sweat smell? Sweat by itself doesnt smell at all. Its the bacteria that live on your skin that mix with the sweat and give it a stinky smell. And when a person reaches puberty, special hormones affect the glands in the armpits these glands make sweat that can really smell.那么，汗水为什么不会有味道呢？汗水本身是没味道的。但皮肤中的细菌和汗水融合一起就不会产生一种臭味。

当人到了青春期之后，就不会在腋窝的汗腺中产生一种类似的激素，使得汗水闻起来有种汗臭味。

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