When Does Piloerection Occur?

The reflex of producing goose bumps is known as piloerection or the pilomotor reflex, or, more traditionally, horripilation. It occurs in many mammals; a prominent example is porcupines, which raise their quills when threatened, or sea otters when they encounter sharks or other predators.

Does piloerection happen when you are cold?

When we're chilly, tiny muscles contract at the base of each hair to make them stand on end, distorting the skin to create goosebumps. All mammals share this hair-raising trait, called piloerection, of using hair or fur to trap an insulating air layer.

How does piloerection keep you warm?

Piloerection (goosebumps).

In response to increased sympathetic nerve discharge, the arrector pili muscles at the base of tiny hairs in the skin contract and cause the hairs to become upright, trapping air and thus increasing the insulating layer of air around the body and minimizing heat loss.