Eilidh Gloyn, of Glen Oroua School, asks :-

Why do we not get goosebumps on our hands, feet and face?

Brian Hyland, a physiologist at the University of Otago, responded.

Goosebumps are caused by the contraction of tiny muscles attached to the base of each hair. In animals with lots of hair or fur, their contraction is enough to lift the hair from lying flat, into a vertical position. This increases the amount of air between the hairs, which increases insulation from the cold. It also reduces the ability of wind to take away that trapped air, which has been warmed by our body heat, and replace it with fresh cold air – the “wind chill factor”. In cold weather these two effects together increase heat retention by the body, in the same way that putting on a jersey does.

In some animals, lifting of the hairs has also evolved a communication function – the muscles are activated by stress or alarm, and send a message – “watch out, I might bite” – and might also help make the animal look bigger and more threatening. You will have probably seen that response if you have a cat or a dog, and even for us humans there is the saying that a scary movie can “raise the hairs on the back of my neck” probably from the sensation produced by the muscles pulling the skin, rather than the hairs visibly lifting. Many scary movies are called “horror” movies, and the word “horror” is actually derived from the Latin word horrere, meaning “hair standing on end”.

Our distant ancestors had lots of hairs, but over the course of evolution, the “hair raising” response has lost it’s importance to us for keeping us warm, and the muscles have become too weak to lift the hairs much. However, they are still there, and are activated by the same things that worked for our ancestors. So in the cold, they contract – but all they are able to do is raise a bump – “a goose bump” in the skin as they tug on the hair at one end, and the small patch of skin they are connected to at the other. It’s called “goose bumps” in English and many other languages because the feathers of a goose grow from bumps on the skin, and when the feathers are plucked those bumps can be seen, and they look similar. This is true for other birds of course, and other languages refer to hen, chicken or just bird-skin for the same thing.

We don't have hairs on the soles of the feet or palms of the hands, so don't get goosebumps there. But we do have hairs on the face, where goosebumps are not prominently seen. Why they are not so prominent on the face is a bit of a mystery. One idea is that perhaps there are so many hairs on the face that all the skin is being pulled every which way by all the little muscles, and so no one bit of it can pucker compared to the next bit. Another possibility is that because the skin on the face is thicker than elsewhere, and the weak little hair muscles are not even strong enough to pucker it.