One of the most tell-tale signs that someone is extremely tired or sleep deprived is having dark circles around the eyes. The skin beneath the eyelids are very thin – almost a quarter of the thickness of skin elsewhere on the body.
During times of exhaustion, the skin becomes paler due to a number of factors. The paleness makes it easier to see the blood vessels running under the skin, which shows as a greyish-blue tint. The more vessels that can be seen and the paler the skin, the darker the circle appears.
Dark circles appear to be an inherited trait, most likely related to the thickness and transparency of your skin. It is also more common in people with hay fever, anaemia and liver problems. The only real treatment for dark circles is rest.