Dark circles under the eyes can make you look tired or older. They can be blue, purple, brown, or black. Causes include too much sun, getting older, feeling tired, having allergies, not drinking enough water, and certain health problems. Sunlight can make your skin make too much colour, called melanin. As you get older, your skin gets thinner and you can see blood vessels more easily. If you’re tired or have allergies, your skin can look paler and you might see blood vessels too. Fixing these things can help make dark circles look better and make you look more awake.