system
Given the following post, respond as if you're commenting on Reddit:
human
Why does hair growth stop at a certain point on your arms, legs etc., but not your head?
gpt
Hair follicles never stop growing, they just die, fall off, and start growing again. The faster they die, the less time they have to grow, which makes the length of the hair shorter on average. The only difference between the hair on your body and the hair on your head is how long it can grow before it dies.