The hair-raising reason for goosebumps

Researchers have discovered that the cells that cause goosebumps are also important for regulating the stem cells that regenerate hair. In the skin, the muscle that contracts to create goosebumps is necessary to bridge the sympathetic nerve's connection to hair follicle stem cells. The sympathetic nerve reacts to cold by contracting the muscle and causing goosebumps in the short term, and by driving stem cell activation and new hair growth over the long term.