What is a goose bump?

A goose bump, also known as horripilation or cutis anserina, is a small, raised bump on the skin that occurs when the hair follicle contracts. Goose bumps are typically caused by cold temperatures, but can also be triggered by fear, excitement, or other strong emotions.

When the body senses a drop in temperature, the arrector pili muscles that surround each hair follicle contract. This causes the hair follicle to pull upright and the skin around it to bulge, creating the goose bump. The contraction of the arrector pili muscles is thought to be a reflex that helps to keep the body warm. When the body is cold, the arrector pili muscles contract to raise the hairs on the skin, trapping air and creating insulation.

Goose bumps are also associated with the release of certain hormones, such as adrenaline (epinephrine) and norepinephrine (noradrenaline). These hormones are produced in response to stress, excitement, or fear and can cause the contraction of the arrector pili muscles.

In some cases, goose bumps can be caused by a medical condition called piloerection, which is a disorder of the autonomic nervous system that causes excessive contraction of the arrector pili muscles. Piloerection can be a symptom of a variety of underlying medical conditions, including diabetes, spinal cord injuries, and certain neurological disorders.