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Why does the skin get gooseflesh? The mechanics of bristly hair

Why does the skin get gooseflesh? The mechanics of bristly hair

August 8, 2022

Goosebumps is one of those phenomena that remind us that the separation between the human being and the rest of the animals is, in the end, a mirage, something artificial. Our body is constantly traversed by hundreds of physiological processes that regulate the way in which we react to our environment, in theory to adapt better to its variations.

Now ... in the case at hand,Why does the skin get gooseflesh and how does this relate to our emotions? Let's see it

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What is goosebumps?

A summary definition of goosebumps is the following: it is a state of the skin in which the body hair is bristling, so that being this hair very thin and short in humans, it seems that tiny "montañitas" appear on the surface of it. The hairs stand on end , but normally we pay more attention to the part of the skin that forms the basis of these.


Straightening of cutaneous hair, known as piloerection in more formal or scientific contexts, is performed by small muscle fibers linked to the base of each hair.

In addition, this phenomenon does not usually occur in isolation, but is related to changes in the states of consciousness and, specifically, in emotional states. In this way, goosebumps have a physiological dimension and another psychological dimension related to emotions . Then we will explore in a little more detail what we know about each of these two facets of the fact of having the hair standing on end.

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The physiological mechanisms of piloerection

It is known that the phenomenon of goosebumps, also known as horripilación, is a vestigial reflex that usually has an adaptive function in mammals in general , since this group of animals are characterized by having hair.


The mechanism by which these protuberances appear on the skin for a short period of time is as follows.

1. Activation of the sympathetic nervous system

This part of the nervous system is the circuit of nerve cells that intervenes when certain stimuli from the environment make us react in a state of activation more intense than normal. For example, it is the type of contexts in which they tend to activate patterns of attack or flight behavior .

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2. Stimulation of the piloerector muscles

These tiny muscle fibers are connected to the sympathetic nervous system and act as a bridge between the latter and the hair follicle, where they are inserted. When receiving the signal from one of the nerves, these smooth muscle fibers contract by pulling the hair upwards.


3. Hair shaft change

In normal state, by default, body hair is arranged obliquely. That is, falling on one side, instead of being perpendicular to the skin. When being tensed by the piloerector muscle, the trajectory of the axis of the hair happens to straighten itself, so that instead of being almost stuck to the skin, it remains in tip. The tension that is generated between the skin that surrounds the base of the hair, on the one hand, and the muscle fibers, on the other, causes a protuberance to appear on the part of the skin through which each hair appears.

Why we get goosebumps: evolutionary functions

As we have seen, goosebumps are something related to the vestigial reflexes that come to us through a line of ancestors that did not belong to our species and that probably had body hair much more developed than us. So, the piloerection could be the difference between having more or less offspring, or between surviving or not doing so . In particular, it has been an advantage for the following reasons

1. Help isolate from the cold

The piloerection appears among other situations when the organism is exposed to cold, so that the body hair becomes more spongy and creates a wider insulating layer between the skin and the environment. In this way, body heat is better preserved .

2. It is associated with situations of danger and reproduction

Another usefulness of goosebumps, at least in our ancestors and in the rest of mammals characterized by having denser and thicker body hair, is to make it easier for the body to look bigger, which is useful in case of that hover near other potentially dangerous animals that may come to doubt whether or not to attack .

At a level of social adaptation, hair bristling is also a quick way to make others aware that there is a danger nearby, as it affects the whole body and, whenever you look in that direction, it is easy to see.

On the other hand, sexual arousal is also capable of producing bristly hair, which can be associated with the need to communicate interest or to point out a certain status . The latter is something that in mammals is intimately linked to reproduction, especially in the case of males.

The case of the human being

In the case of humans, the range of sensations that we can have is more varied than that of most mammals, since our mental processes are very enriched from contextual information articulated from abstract thinking.

Therefore, goosebumps can appear in many situations in which a very intense emotion invades us, such as listening to music, being touched by a person, or even listening to a speech or reading a book. In this case, the evolutionary utility loses its relevance: the bristle of hair does not have a certain function, it simply exists as a consequence of a process of natural evolution that has led to us (in the case of our evolutionary line).


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