If you feel insulted and offended when people tell you that you look tired, it's because you should feel insulted and offended. Back in 2010, a Sweden-based research team published the results of a study that showed that people who appear tired are perceived to be unhealthy and unattractive.
Recently, that research team published more details in Sleep indicating that sleep deprevation can affect the human face, making people appear unattractive and sad.
Doctoral candidate Tina Sundelin and her team photographed research subjects on two separate occasions: Once after eight hearty hours of sleep, and then once after 31 hours awake. Forty people then rated the photographs on scales for fatigue, sadness, and ten metrics of physical appearance.
The eyes of sleep-deprived individuals bore the greatest burden. Subjects were perceived as having "more hanging eyelids, redder eyes, more swollen eyes and darker circles under the eyes." People also perceived sleep-deprived subjects as being sadder and having paler skin, more wrinkles or fine lines, and "more droopy corners of the mouth."
Nap time? Nap time. [The Atlantic]