Dark circles under the eyes is a very common complaint! The skin under the eyes is very delicate and thin. This means that the blood vessels under this skin show through easily, which gives the dark discoloration. As we age, our skin becomes even thinner. As such, it is very common for the problem of dark circles to worsen as we get older.
Occasionally, the dark circles can be the result of a medical problem causing congestion of blood in this part of the face. The medical conditions that are most commonly associated are chronic allergies (of the nose or eyes) and sinus congestion. Therefore, if you haven't done so already, it might be worth a visit to your primary care doctor
. They can quiz you to see if you have any symptoms consistent with these conditions and they can also perform a physical examination to rule them out. If you do have one of these conditions, then they can usually be easily treated with common medications, like anti histamines. You should notice an improvement in the discoloration with successful treatment.
I would suggest making an appointment with your primary care doctor at your earliest convenience.