Goose flesh, more commonly called goosebumps, is a condition in which the skin at the base of individual hairs stand up or appear swollen, giving the skin a bumpy appearance. It is generally caused by the nervous system during the fight-or-flight response or during times of cold, sexual arousal, or sometimes disease. Once the stimulant is over, the skin generally returns to normal.
When the muscles beneath the hairs contract, it results in each individual hair standing on end. Bumps seems to appear beneath them, and the skin takes on a bumpy or pointy look and feel. The skin may also feel more rigid to the touch. This is a benign condition and causes no harm to the body. There is no way to reduce the appearance of goosebumps aside from warming the skin or removing the threat, or assumed threat, causing the response.
The term goose flesh stems from the fact that geese have a similar bumpy appearance on skin where feathers have been removed. For geese, this is a permanent state and is not caused by a stimulant. Many animals, including geese, have also have the same skin response when startled or threatened or when cold. Goosebumps have necessary functions when exhibited in wildlife, however, whereas in humans they serve little purpose.
Most mammals have the goose flesh response, as well as some birds and other species. This serves to keep them warm by forming a layer of insulation around the body by holding warm air in. Animals with thick fur may also exhibit this response when threatened because it makes them appear larger, helping ward off enemies. These explanations are only hypotheses as to why this occurs, and it is entirely unknown why goosebumps occur in humans, although it may stem from prehistoric man's need to appear larger against predators.
There are certain diseases which may cause goose flesh as well, including brain tumors and epilepsy. If goosebumps begin occurring without explanation, it is a good idea to get an exam by a medical professional. This is especially worrisome if other symptoms are present.
Sometimes withdrawal from certain medications and recreational drugs may also cause goose flesh to appear. Heroin and opiates are two examples. This is generally a temporary condition that goes away once the drugs are out of the system or the user takes a dose of the drug. Other symptoms are also generally apparent.