Why do we get goosebumps?

You step out of a warm bath, or you watch a spooky bit of a film, and suddenly your arm is covered in tiny bumps. Where did they come from?

Tiny muscles pull your hairs

All over your skin grow thousands of tiny hairs. At the bottom of each hair sits a teeny muscle. When you feel cold or scared, your body sends a quick signal, and these little muscles squeeze tight.

When a muscle pulls, it tugs its hair to stand straight up. The skin around the hair puffs into a little bump. Lots of bumps together are what we call goosebumps — because they look like the skin of a plucked goose!

An old trick from furry animals

Why would your body do this? The answer is hidden in the past. Long ago, our animal relatives were covered in thick fur.

When a furry animal is cold, its standing-up hairs trap a layer of warm air, like a fluffy blanket. When it is scared, all that puffed fur makes the animal look bigger to scare an enemy away. Cats still do this — a frightened cat puffs up its tail!

We have only thin hairs now, so the trick does not really warm us. But our body still tries.

Wonder fact: You cannot make goosebumps appear just by wanting them — but some people get them from beautiful music!