Heredity is one of the main reasons that produces dark circles under the eye. This cannot be reversed but there are other life-style related factors like lack of sleep, an imbalanced diet which lacks nutrients, fatigue. age, hormonal changes which can cause or aggravate this condition.
These are nothing but blood vessels that can be seen through the skin. The skin around the eyelids (periorbital skin) is the thinnest skin in the body. When blood passes through the large veins close to the surface of the skin it can produce a bluish tint. The more transparent the skin -- also an inherited trait -- the darker the circles appear.
Apart from home-made ingredients like almond oil - honey massage around the eyes and tea-bags, you can drink plenty of fluids and get adequate rest.
The Preparation H version with phenylephrine HCl 0.25% will constrict the capillaries resulting in the temporary reduction of the appearance of dark circles.
People have told me to use baby oil, olive oil and Ambi. I have heard about Preparation H but thought it was a myth or just for puffiness under eyes.