Goosebumps
Also called: Piloerection · Cutis anserina · Gooseflesh
Tiny muscles at the base of most hairs pull the hair upright when you are cold, scared, or moved. In a furry animal this traps warm air or makes it look bigger. In a human the raised hair does almost nothing.
How common
Does this happen to you?
How it works
Every hair on your body sits in a follicle. Most follicles have a tiny strip of smooth muscle attached. This is the arrector pili muscle2. When it contracts, it tilts the hair upright and pulls on the skin around it. The skin dimples into a small bump. Across an arm or a leg, many of these bumps appear at once1.
The muscles are driven by the sympathetic nervous system, the fight-or-flight system. You cannot choose to fire them, except for a few unusual people1. Three common kinds of trigger set them off1:
- Cold. The skin senses a drop in temperature.
- Fear or shock. A sudden threat, a loud sound, or a fright.
- Strong emotion. Music, a speech, a film scene, or a memory. This version is called frisson, and it often comes with a shiver down the back3.
In a furry animal all of this makes sense. Raised fur traps a thicker layer of still air next to the skin, which keeps the animal warm. Raised fur also makes the animal look bigger to an enemy. A cat facing a dog does exactly this1. Humans have kept the muscles and the nerves but lost most of the fur. The reflex still fires, but the effect is now almost nothing. Some call it a vestigial reflex, a leftover from ancestors1. In mice, the same muscle and its nerve also help control the stem cells that regrow hair4.
The name comes from the look of a plucked goose. The Latin term cutis anserina means the same thing1.
Is it a problem?
No. Goosebumps from cold, fear, or music are a normal reflex12. They cause no harm. They are rarely a sign of illness on their own. Some conditions, such as temporal lobe epilepsy, can cause them1. Goosebumps that come with chills, a fever, and feeling generally unwell usually point to the body fighting an infection, but it is the fever that is worth watching, not the goosebumps. See a doctor if shivering and goosebumps come with a very high temperature or will not settle.
History and culture
Many languages name the effect after a plucked bird. In French it is chair de poule, chicken flesh. In Japanese it is torihada, bird skin1. A small number of people can raise goosebumps at will, with no cold or emotion involved. This is covered in its own entry.
Sources and further material
- Wikipedia Goose bumps
- doi.org Cell Types Promoting Goosebumps Form a Niche to Regulate Hair Follicle Stem Cells Cell. In mice, the arrector pili muscle and its nerve help control hair follicle stem cells.
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Related oddities
Voluntary piloerection
Giving yourself goosebumps on command, without music, cold, or fear. Nobody knows how many people can do it, but it seems rare. The muscles involved are not supposed to take orders.
Frisson
A wave of chills up the back, sometimes with goosebumps, at a powerful moment in music, a film, or a speech. It is thought to come from the brain's reward system reacting to an expectation being met or broken.
Random shivers
A single brief shudder that runs down the spine or through the whole body when you are not cold. Many people report them. Nobody has counted them.
Blushing
When you are embarrassed, blood vessels in the face open wide and the skin turns red. You cannot stop it. Darwin called it the most human of all expressions, and no other animal is known to blush from embarrassment.