• Written by Nigel Taylor, Associate Professor of Thermal Physiology, University of Wollongong

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!

What exactly happens in the body when we sweat? – Bianca, age 9, Sydney

Hi Bianca, thank you for your question.

Sweat comes from special parts in our skin called glands. You might be able to see them if you have a very strong magnifying glass.

Try to find lines on your skin, and look where those lines meet. There you will find a sweat gland – we are born with about 2 million of them.

When we get hot, sensors in the body tell the brain. The brain then tells the sweat glands to work, and we sweat. That sweat is salty as it comes from the salty fluid found inside our bodies. We are 60-80% water. If that sweat can evaporate, we will cool down. This is why humans sweat.

Because dogs and cats do not sweat like humans, panting and fur licking helps them to stay cool. Marcella Cheng/The Conversation, CC BY-ND

Do you have a dog, Bianca? I bet you know what dogs do when they get hot; they pant. They take many small breaths and hang their tongues out. Gross! When they pant, water drops fall onto their fur. When those drops evaporate, they cool down. We often see cats licking their fur. Because dogs and cats do not sweat like humans, panting and fur licking helps them to stay cool. Cats always think they are cool.

All healthy humans sweat. We do this for two reasons: either because we are hot and need to cool down, or because we are stressed.

How does sweat cool us down?

Think about water, ice and steam. Did you know they are all just water?

Water looks different depending on its temperature. Ice is frozen or solid water. Steam is heated water that has turned into a gas called water vapour.

Try this experiment: lick the back of your hand and then gently blow air over the wet skin. What do you notice? It feels cool, right?

Blowing on your skin makes the water turn into water vapour. The word we use when this happens is “evaporation”. Evaporation helps take away heat.

Read more: Curious Kids: How do we get allergic to food?

Why else do we sweat?

So what about that other type of sweating I told you about?

Do you get nervous when you have to speak about something in front of your class at school?

In my job, I have to speak to other scientists at special meetings called conferences. I get nervous about that. Sometimes, I get so nervous that I get sweaty.

Some people get sweaty hands, some get sweaty under their arms and some just sweat all over. I am in the last group. We call this nervous sweating.

Sweating can also happen during an exam or when we are concentrating hard on something important. We don’t know much about this type of sweat, but we do know that it comes from the same sweat glands.

Sometimes, we get so nervous that we get sweaty. Marcella Cheng/The Conversation, CC BY-ND

Thank you again for your question Bianca, and I hope my answer is helpful.

Read more: Monday's medical myth: you lose most heat through your head

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