system
Given the following post, respond as if you're commenting on Reddit:
human
Why do people 'look' tired? What actually happens to our faces (physically) when we've gone without sleep for a substantial amount of time?
gpt
Primarily a combination of dehydration, blood vessel dilation, and hormone levels due to your body missing out on its regular re-calibration and balance mechanisms during sleep. The dehydration causes your skin to lose plumpness and elasticity from the inside, making it sag slightly and appear less smooth. The blood vessel dilation causes more of the darker blood to show through the thinner parts of your skin, causing blotchiness and dark under-eye circles. Cortisol levels also increase, causing low-grade inflammation that can exacerbate skin conditions like acne.