Goosebumps are small bumps on the skin caused by the tension of the muscles, which pull the body hair into an erect position. In humans, these bumps are a vestigial reflection, left over from a time when humans had more hair; A wide variety of animals demonstrate this interesting reflex in response to certain stimuli. Many people have experienced goosebumps at some point in their lives, and some may have wondered why they appear.
There are two main reasons why goosebumps appear: cold and fear. In animals that actually have fur, standing individual hairs up in cold weather is a sensible course of action, as the erect hairs can trap air, adding a layer of insulation to protect the animal from the cold. In the case of fear, goosebumps on an animal with fur would make the animal look larger, which could intimidate the threatening animal and give it a chance to run or fight.
The medical term for this reaction is cutis anserina , and the term "horrorization" is sometimes used to refer to the act of raising goosebumps. This reflex is part of the body's "fight or flight" system, which means it is completely involuntary. It's triggered by a signal from the autonomic nervous system, which tells the muscles around the hair follicles to tighten, lifting the hairs and creating a distinctive tight bump. They're common on the arms and legs, but goosebumps can technically appear anywhere, including the face, scalp, and chest.
Various colorful slang terms are used to refer to goosebumps, including goosebumps, goosebumps, goosebumps, and goosebumps. The abundance of bird-related slang is a reference to the plucked skin of geese and chickens, which often has a similar raised pattern. Because birds don't actually have hair, geese don't technically get goosebumps.
As a general rule, goosebumps are not a cause for alarm, although the situation that is causing them could be a potential source of concern. However, they are sometimes associated with certain medical conditions, particularly those involving the brain, so someone who suffers from them a lot or for no apparent reason may want to seek medical attention. They are also common in people experiencing drug withdrawal.