Why do we sweat?

Think about the last time you ran and ran on a warm, sunny day. Your forehead felt wet, and your shirt stuck to your back. If a drop touched your lips, it tasted salty.

That wet, salty water is sweat. Nobody poured it on you, so where did it come from? Why do we sweat?

It all starts with heat building up inside you. Your muscles make heat whenever they work hard, like when you run, jump or climb. On a hot day, the sun warms you from the outside as well.

Your body works best when it stays just warm, not too hot. Your brain keeps watch on how warm you are. When you get too hot, your brain sends out a message to cool you down.

That message goes to your sweat glands, which are tiny tubes deep in your skin that make sweat. You have millions of them, all over your body, from your forehead to the bottoms of your feet.

Your sweat glands take water from your body and push it up through tiny holes in your skin. The water spreads out over your skin as sweat. What do you think happens to those wet drops as you keep playing?

The sweat from your sweat glands dries up into the air. As each drop dries, it takes heat away from your skin with it. That is why wet arms feel cool in a breeze after a swim.

Your skin cools down, and so does the blood flowing just under it. That cooler blood travels all around your body. Bit by bit, it helps cool you from the inside too.

Sweat glands. When your body gets too hot, your brain tells your sweat glands to push water onto your skin, and as that sweat dries, it carries heat away and cools you down.

So the next time you feel sweaty after playing, you will know your body is busy keeping you cool and comfy.