Why do we get dark circles under our eyes?

The skin of the lower eyelid is among the thinnest on the body, often around half a millimetre, so the bluish colour of veins underneath shows through easily. Genes play a big role, and in many people with darker skin tones the circles come from extra pigment, known as periorbital hyperpigmentation. With age, the skin loses collagen and the fat pads beneath the eyes thin out, creating hollows that cast shadows. Allergies and congestion can swell nearby vessels, producing so-called allergic shiners. Lack of sleep does not cause circles directly, but it makes skin paler and puffier, and a 2013 study found sleep-deprived people were rated as having darker circles and more tired-looking faces.