system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do animals go grey/lose follicle pigmentation around their mouths before other parts of their body?

Both humans and other animals seem to go grey around their mouths before other parts of their body, why is that?
gpt
Melanocytes, which produce pigment, are unevenly distributed in the body. As an organism ages, melanocytes become less effective and produce less and less pigment. Regions that have less melanocytes go grey first. In humans the area with the lowest number of melanocytes is around the temple,  in dogs the nose, and cats have more or less evenly distributed melanocytes and typically don’t go grey but slowly fade in color over time.