If you get dark circles under your eyes when you're tired--and I know I do--this is not because of the tiredness itself.

Now some of this is based on genetics, some people just inherit darker circles under their eyes. And your under eye can be naturally darker or it can have thinner skin, and in the latter case you would see the blood under your skin more easily so the area under your eyes would always be darker than other parts of your body with thicker skin.

But if you only get them when you feel tired, it could be because you're touching your face a lot. When you are tired and rubbing your eyes a lot you're putting pressure on the lower eyelid skin and you can actually burst blood vessels in that very delicate area, so dark blood colors it. Rubbing your eyes can also trigger allergies which prompt an immune response that puffs up your eyes and that puffiness can cast shadows over the area.

So if you want brighter eyes and you don't want to mess with like a whole makeup situation, just touch your face less. Or, or you should get some more sleep. Put the phone down.