Dark circles under the eyes are often associated with lack of sleep, but there are many other factors that can contribute to this feature. Some causes include dehydration, anemia, allergies, sun overexposure, skin conditions, eyestrain, aging, and genetics. Fortunately, many of these causes can be treated or managed. To prevent dark circles, try applying cold compresses, using cold caffeine tea bags, placing cucumber slices over the eyes, protecting yourself from the sun, reducing alcohol and tobacco intake, watching your diet, using moisturizers, and getting enough sleep. Remember, dark circles under the eyes can be more than just a sign of fatigue.