Imagine you are coming out of a swim in the sea. It’s a beautiful day, the temperature is perfect but it’s getting dark and there’s a little cool breeze. As you throw your towel over your shoulders, you realize that the hair on your arms is standing on end.
The same thing happened to you at a friend’s birthday party, when your partner held your hand for the first time or when you heard that song that moves you live.
It has happened to you, hasn’t it? It’s what is commonly known as ‘goosebumps’, a bodily reaction that is associated with cold and intense emotions and that apparently has no reason to exist. Why does our body react in this way? Does it have an evolutionary or survival explanation? Does the same thing happen to other animals?
Why do people get goosebumps?
Goosebumps are caused by the release of adrenaline, which is secreted in cold and stressful situations. This hormone produces a series of reactions throughout our body and puts it on alert so that it can fight or flee if it is in danger.
It is also responsible for suddenly increasing our strength or making our mental capacity to respond more agile. Hence, it also comes out when we listen to music, gets excited or are afraid.
When the outside temperature is low, the capillary hair stands on end. This occurs on the entire hair surface, except for the hair covering the genitals, hands or feet. At the root of the hair, under the skin, hides a small erector muscle which, when contracting, creates a layer of air around the body that protects it from the cold.
This phenomenon is also called piloerection and refers to the involuntary development of bumps on the skin, at the base of the body hair, when we are exposed to situations or sudden changes in temperature. This pilomotor reflex occurs in many mammals, in addition to humans, although most of the time we think that it only affects us.
According to George A. Bubenik, physiologist and professor of zoology, explained to the magazine ‘Scientific American’, it is a response inherited from our ancestors.
Other species also experience something similar and its purpose is to insulate our body and shelter us from the cold outside. In fact, our ancestors had a body full of hair and this response served to protect them.
Why does the skin hair stand up?
The reasons why our hair stands up and the skin changes its texture are varied. Some of the main ones we highlight are:
- Touching certain surfaces.
- Low temperatures.
- Alteration in the mood.
- Sexual excitement.
While most of these are related to a drop in body temperature, sometimes the skin becomes flushed by the opposite. For example, sexual stimuli.
This reflex has been with man since ancient times, although the body used to be more covered with hair. As is the case with many furry animals, this mechanism is useful for maintaining body heat. When the hair stands up, the coat swells and provides a much greater insulating layer.
One of the triggers for “goosebumps” is fly or fight. And there is also a response to it. When a threat is presented, the first human reaction is to fly. In some cases, they choose to fight against that danger.
Thus, provides a sense of grandeur and intimidation towards the opponent. Cats, bears or Kingy’s lizards, use similar contraptions to appear more threatening to enemies. For males, bristling body hair is a sign of power and lack of fear.
The sympathetic nervous system is responsible for this, as it regulates the contraction of muscles and the secretion of various glands. Its function is to make the human body act when faced with a situation that implies danger. Normally it is activated when the nervous system detects that the person is in a situation of conflict or anxiety and therefore must flee.
To facilitate the flight response to some external and foreign issues, the heart rate increases, the pupils dilate, the blood vessels dilate, the bronchi of the lung dilate and there is a considerable increase in blood pressure.
The message of a possible threat is detected thanks to two of the most important neurotransmitters of the sympathetic system: adrenaline and noradrenaline.
However, this reaction can occur even when we are not in a dangerous situation since it is common for the sensation to be experienced when very happy, unexpected or exciting events occur; for this reason, the phenomenon is accompanied by a tingling sensation that runs all over the skin.
Where are we most likely to bristle? The areas most likely to go through piloerection are:
- The forearms.
- The legs.
- The neck.
- The head.
- The nape of the neck.
- The face.
What about shivering?
Another reaction that happens in our body related to low temperatures is called shivering. How does it differ from “goosebumps”? The latter is produced by several causes and the former, only, by cold or heat (it also appears when we have fever).
The most frequent symptoms are shivering and pallor. It can be accompanied by bluish lips and shivering teeth.
If the person is exposed to a cold environment or his body temperature rises above 39 °C, chills appear. They are frequent in the early stages of infections and in patients with malaria.
Finally, an interesting fact: people in Siberia (one of the coldest places in the world) do not usually get goosebumps due to low temperatures. This is because they are genetically adapted to these conditions. Even though they are thin, they have a special fat that shelters them from snow, freezing wind and adverse weather.
In 2020, in an analysis of mice, published in the scientific journal ‘Cell’, scientists from Harvard University (USA) discovered that specific muscles that contract when goosebumps appear are connected to the sympathetic nervous system. When low temperatures are detected, they bridge the gap between the sympathetic nerves and the hair follicles.
In the short term, it makes the hair stand up and goosebumps appear; in the long term, it seems to promote hair growth. The researchers argue that this is an important link between stem cells, which the body can use to create other cell types, and external stimuli.
So, while the nerve-muscle connection was already known in this specific system, the link with hair-regulating stem cells is a new discovery, and an unusual one, since neurons, tend to prefer connections with other neurons or synaptic-type connections with muscles.
So, why do people get goosebumps?
Piloerection, popularly known as goosebumps, is a reaction of our organism – specifically of the sympathetic nervous system – in which the hair stands up and the skin takes on a granular appearance – similar to the skin of birds after being plucked, hence its name – and which occurs as a result of a sudden drop in temperature, but also when we experience intense emotions.
As you can see, the so-called “goosebumps” are a normal reaction of the organism to certain stimuli, many of them related to temperature changes. In ancient times it was a reflex that helped men to keep warm, however, today it lacks any real usefulness.
As society is so diverse, complex and different, what gives someone fear, nerves or stress will not be the same thing that causes these reactions in other people, that is why it is very ambiguous to specify the actions that originate the goosebumps.
Biology clarifies that this stimulus has accompanied the human being since ancient times and endures in current generations as a symbol of evolution.
It is argued that it was a reaction that occurred to increase body heat since in the past people had much more hair, the organism made this happen to keep them warmer, just as it happens with animals today.
Cutts, J., Lee, G., Berarducci, M., Thomas, C., Dempsey, P. K., & Kadish, S. P. (2002). Goosebumps. The Lancet, 360(9334), 690.
Shwartz, Y., Gonzalez-Celeiro, M., Chen, C. L., Pasolli, H. A., Sheu, S. H., Fan, S. M. Y., … & Hsu, Y. C. (2020). Cell types promoting goosebumps form a niche to regulate hair follicle stem cells. Cell, 182(3), 578-593.