Dark circles under the eyes generally refer to the hyperpigmentation of the skin primarily below both eyes. They may occur due to medications, poor diet, pregnancy, menstrual disorders, chronic stress and lack of sleep. Dark circles under the eyes are not always a sign of weariness, but stress and exhaustion seem to aggravate the facial appearance of many people. The common signs of dark circles include- dark coloration of the skin under the eyes, tiredness from sleep deprivation (insomnia), stress, and fatigue. One may also notice puffiness and eye bags under the eyes. If darkness and swelling appear under just one eye and seem to compound over time, you must seek medical attention.