What causes goose pimples?

Goose pimples, scientifically known as piloerection or cutis anserina, are small bumps that appear on the skin when a person feels cold, scared, or excited. They are caused by the contraction of tiny muscles called arrector pili, which are attached to the hair follicles.

When the arrector pili muscles contract, they pull the hair follicles upright, causing the skin to pucker. This traps a layer of air near the skin's surface, which acts as an insulating barrier. This is an evolutionary response aimed at preserving body heat in colder temperatures.

In the past when humans had longer hair, the contraction of the arrector pili muscles would cause the hairs to stand on end, making them appear larger. This might have been a defensive mechanism meant to make humans look bigger and fiercer to potential predators or rivals.

Goose pimples can also occur in response to strong emotional triggers, such as fear, surprise, or sexual arousal. In these cases, the arrector pili muscles contract due to the release of certain hormones, like adrenaline.