system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do eyelashes stay colored for so long while other body hairs go gray quicker?
gpt
Hair is always falling off and regrowing. Eyelashes don't do this as often as the hairs on your head. Hair turning gray is a result of the natural cycle of the hair follicle over your lifespan. 

As the cycle continues, your hair produces less color, turning gray. This process usually begins after age 35.

Other factors such as vitamin deficiency, stress, and genetics also play a role to when your hair starts losing color.

In some ways this is similar to cancer being more likely to occur the older you are. As cells divide, they lose a bit of themselves that keep them from turning into cancer. Over time, it accumulates and has a higher chance of turning into a cancer cell.