Why Do We Get Goosebumps? A Cold-Weather Reflex With a Hidden Job

A cold breeze, a sudden chill, and the skin on your arms turns bumpy. Goosebumps are so familiar that the odd part is easy to miss: in humans, they barely help.

What happens in the skin

According to the US National Institutes of Health, goosebumps occur when tiny muscles in the skin's hair follicles, called arrector pili muscles, pull hair upright. Earlier research identified three cell types that work together to make this happen: the arrector pili muscles, sympathetic nerves and the hair follicles.

Why it helps animals but not much us

NIH says that in animals with thick fur, standing hair helps keep them warm. In people it does not do so, because we have relatively little body hair. Yet humans still produce goosebumps when cold. That puzzle is old. Harvard's news service notes that Charles Darwin wondered about goosebumps in his writings on evolution.

A possible second job

In July 2020, researchers led by Ya-Chieh Hsu at Harvard and Sung-Jan Lin at National Taiwan University published a study in the journal Cell. Working with mice, they found that the same cell types that cause goosebumps also help regulate the stem cells that regrow hair.

Harvard describes it this way: the sympathetic nerve reacts to cold by contracting the muscle and causing goosebumps in the short term, and by driving hair follicle stem cell activation and new hair growth over the long term. NIH adds that removing the sympathetic nerves from mouse skin delayed stem cell activation and new hair production, and that the chemical norepinephrine was involved. The muscle bridges the nerve's connection to the stem cells.

What this does and does not show

This was work in mice. NIH says the findings may have implications for hair loss and for understanding wound healing, but it presents them as possibilities. The study does not show that goosebumps treat hair loss in people.

Sources

• NIH Research Matters, What goosebumps are for: https://www.nih.gov/news-events/nih-research-matters/what-goosebumps-are
• Harvard Gazette, The hair-raising reason for goosebumps is revealed: https://news.harvard.edu/gazette/story/2020/07/the-hair-raising-reason-for-goosebumps-is-revealed/

Facts checked: October 8, 2026.