Dark circles are caused by hyperpigmentation, that is, a higher-than-average amounts of melanin, the substance that gives your skin its pigment. They tend to show up in people of Mediterranean descent and can run in families. In other words, if your parents have them, chances are that you will too. Dark circles can occur due to fatigue, allergies, overexposure to the sun, menstruation or pregnancy.
Sometimes what you’re seeing isn’t really darkened skin, but rather engorged blood vessels under your eyes. Because the skin under your eyes is thinner than skin anywhere else on your body, blood vessels there are more noticeable, especially if you’re fair-skinned.
If you want to try to minimize dark circles, you might apply a cold compress. Close your eyes and cover them with a cold washcloth for about five minutes. That will help constrict your blood vessels, minimizing darkness and it may help to minimize tissue swelling and eliminate some of the darkness.
You might also try alpha hydroxy acids. The most common alpha hydroxy acids are glycolic acids (extracts derived from fruit and other plants). These help smooth the skin and eliminate the older top layers of skin.