Q: What are goose bumps and what causes them to appear on the skin?

A: Interesting question. Well, if you’ve ever been in an air-conditioned New York City bus on a hot summer day, you know that goose bumps can be caused by extreme cold (that’s because there are only two settings for the air conditioning on NYC public transportation — “Icebox” or “Heat Wave”). If you’ve ever been chased by a bear, you also know that goose bumps can be caused by fear. But how?

Goose bumps are a phenomenon caused by the sympathetic nervous system, which controls our fight-or-flight response. When you encounter a dangerous situation, such as a bear approaching you, your sympathetic nervous system sends more blood to your brain, slows digestion, and causes your pupils to dilate — all things that will help you either “fight” or “take flight.”

Goose bumps are one of those fight-or-flight responses of the sympathetic nervous system. When you experience cold or fear, for example, a nerve reaction is sent to the muscles that control the hair follicles on your skin, which cause them to contract. This muscle contraction causes the hair follicles to elevate above the skin (and your hair to stand erect) and resemble the bumps on a goose’s skin after its feathers have been plucked — hence the name goose bumps (other names for goose bumps include goose flesh or goose pimples). The medical term for goose bumps is cutis anserina, coming from the Latin for the word goose. Even weirder sounding? The name for the reflex that causes goose bumps to occur is horripilation (a combination of the Latin words meaning “to bristle” and “hair”).

But how is this helpful to us as an involuntary response to cold or fear? Well, back in the days when our ancestors may have had a lot more hair, this might have helped to keep them warm or scare an oncoming predator. These days, though, goose bumps are what is known as a vestigial reflex, left over from the days of yore even though no longer useful. Goose bumps, or the reflex that causes them, also occur in many other mammals and is still very useful for them. For example, when a porcupine encounters a predator, its quills will bristle as a means of intimidating the enemy. Some furry animals’ hair will stand on end when they are cold because this allows them to trap more air between their hairs, providing another layer of insulation.

Interestingly, goose bumps can also be caused by drug withdrawal, which is where the term “going cold turkey” comes from — an addict who suddenly stops using drugs can experience cold sweat, clammy hands and goose bumps — much like the way a cold (dead) turkey will feel.

So there you have it — the scientific explanation for where goose bumps come from and why they exist. So next time you have a particularly chilling experience (whether it be because you’re actually cold or scared out of your wits), remember that those goose bumps are there to help…or at least they used to be.

What exactly are goose bumps?
What exactly are goose bumps and what causes them to appear on the skin?