Why do my hairs stand up when I'm cold?

Think of a furry animal. When its hairs stand up, its fur fluffs out and holds a thicker layer of air next to its skin, and that air keeps warmth in. People don't have a thick furry coat, so standing our hairs up hardly warms us at all. We still get the bumps, though!

Then why do I get goosebumps when I'm scared?

When you feel cold or afraid, your body lets out a chemical called adrenaline, and it makes those hair muscles tighten. For a furry animal, that's handy. A frightened cat puffs up its fur so it looks bigger, and a dog might back off. Our bodies do the same thing, so a spooky story can give us goosebumps.

Why do we get goosebumps?

Clover answers for ages 4–11, then goes 2 steps deeper each time a child asks why.

Clover says

Lots of your skin has tiny hairs, and each one has its own little muscle that can pull on it. When you get cold, those muscles tighten and pull the hairs up straight. Little bumps pop up on your skin around them. Those are goosebumps!

For ages 4–7

Checked against Your Skin (KidsHealth)
Why do my hairs stand up when I'm cold?

Think of a furry animal. When its hairs stand up, its fur fluffs out and holds a thicker layer of air next to its skin, and that air keeps warmth in. People don't have a thick furry coat, so standing our hairs up hardly warms us at all. We still get the bumps, though!

For ages 6–9

Checked against Why do humans get goosebumps? (Scientific American)
Then why do I get goosebumps when I'm scared?

When you feel cold or afraid, your body lets out a chemical called adrenaline, and it makes those hair muscles tighten. For a furry animal, that's handy. A frightened cat puffs up its fur so it looks bigger, and a dog might back off. Our bodies do the same thing, so a spooky story can give us goosebumps.

For ages 8–11

Checked against Why do humans get goosebumps? (Scientific American)