We’ve all felt that peculiar sensation that comes with goosebumps. It might be a chilly breeze that causes your arm hairs to stand on end, or maybe a shadow in the dark that catches your imagination. Either way, goosebumps are the odd reaction we have to a variety of stimuli — but what are they exactly? And what do they have to do with geese?

Inherited heat retention system

Legs with goosebumps
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The name goosebumps, the common term for what is known in the medical communities as piloerection, comes from the resemblance of skin to that of a plucked bird during the reaction. Goosebumps are caused by contractions in small muscles that are connected to hair follicles, creating a depression on the skin’s surface, resulting in the hairs standing upright.

It is believed that this is an inherited trait from our ancestors, who had thicker coats of body hair. You can see the reaction performed usefully in common domesticated animals such as cats and dogs. By standing their thick fur on end, it creates a layer of insulated air, which helps keep the animal warm in addition to the passive heating properties of the hair itself.

While our layer of body hair is too thin to make this insulation process effective, the muscle contraction and increased electrical activity does help to stimulate the body, which is why goosebumps go away when you warm up.

Physiological reaction

Goosebumps are also associated with a wide variety of situations, from frightening to emotional. People talk about feeling goosebumps at their wedding, after watching a particularly high stakes sporting event, and even from recalling a strong memory. If goosebumps are intended to warm us up, why do we also get them in reaction to emotional states?

Think back again to the example of a common house pet. When a cat gets into a situation that triggers its fight or flight reaction, such as being approached by a dog or larger cat, its hair will stand on end as it arches its back. This is all in order to appear larger than it actually is in order to deter the dog from a potential attack.

In the same way, goosebumps in humans are also triggered by the subconscious release of the testosterone hormone. When high level of stress, whether positive or negative, occur testosterone is released to help in the fight or flight decision making process. This cues goosebumps, and we start to feel our hair prick up.

Are goosebumps dangerous?

Persons arm with goosebumps
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In general, goosebumps come and go without causing any sort of issue or lasting effect. However, there are some situation where goosebumps may be an indication of a more serious problem. These include:

  • Atonomic dysreflexion– This condition is a result of a spinal cord injury that causes an overreaction of the body’s nervous system.
  • Keratosis pilaris – This skin condition is what occurs when goosebumps don’t go away like normal, and instead continue for an indefinite period of time. While unsettling, this condition in general does not cause any adverse effects.
  • Temporal lobe epilepsy – Chronic goosebumps can also be caused by this disorder brought on by repeated seizures.
  • Chills – While we all get goosebumps when it’s cold out, getting them when it is not cold may be a sign of body temperatures that are out of order, such as when a flu is coming on.

Are there any other situations that can cause goosebumps?

Since goosebumps are part of a sympathetic nervous systems, sometimes you may get goosebumps from simple physical exertion. Vocal stimuli, such as dialogue in a movie or a song that affects you emotionally, may trigger goosebumps.

Goosebumps may be a little mysterious, but in general, all you need to do when you feel them is to take  a deep breath, relax a little, and maybe put on a sweater.