system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does a lack of sleep give people bags under their eyes?
gpt
It's the extended strain on your facial muscles from having to keep your eyes open for longer than they normally should be open. Note: this isn't the *only* reason for eye bags/circles, it's also genetics, dehydration, allergies, and too much sodium.