​​Why does your hair stand on end when you get cold?

Tiny Muscles connected to each hair Follicle contract, causing the skin to bulge and our hairs to stand on end. Back when we were covered in more hair this allowed us to trap as much air as possible which worked as an insulator to battle the cold. It’s also known as experiencing Goosebumps. They also form when you experience a strong emotional feeling, such as extreme fear, sadness, joy, and sexual arousal. Goosebumps may also occur during times of physical exertion, even for small activities, like when you're having a bowel movement.