lack of iron is a common cause of dark circles under your eyes since iron in our bodies carries oxygen and having a lack of iron means that your cells don't receive enough of the needed oxygen.
The lack of oxygen can cause the cells under your eyes to look dark and having an iron deficiency can cause skin to have an ashy or pale look to it.
To get rid of the dark circles you can take some lemon juice from a lemon and apply it to a cotton ball and then apply the lemon juice to the dark circles and let it sit there until the lemon juice dries.
The lemon juice contains natural acid that will help get rid of the dark circles.
Apply the lemon juice daily until the dark circles are gone.