There are many causes for dark circles under the eyes, the most common ones are : Hereditary reasons, the more transparent your skin, an inherited trait, the darker the circles appear. It could also be because you have inherited certain facial features (e.g. If you have deep-set eyes). Allergies - Any hidden allergies release histamine which makes the blood vessels more inflamed. Nasal congestion - the veins from the eyes drain into the veins of the nose. If the nose is blocked up, the veins around the eyes become larger and darker. Medications - Any medications that you are taking that causes blood vessels to dilate, can cause circles under the eyes to darken. Because the skin under the eyes is very delicate, any increase blood flow shows through the skin. Ill health - Appearance of dark circles may indicate problems or weakness in the kidney or liver activity. Exposure to the sun - Sun exposure, which triggers the skin pigment melanin to increase, may result in a darker appearance.
Iron deficiency - It is believed that lack of mineral iron can cause dark circles as well. Iron deficiency is the most common type of anemia and this condition is a sign that not enough oxygen is getting to the body tissues.

Treatment of dark circles under the eyes can be very challenging, especially for long term symptoms. It is important to identify the underlying cause instead of wasting money for expensive creams that may actually make the symptoms worse (e.g. if you are allergic to any of the substances used in those fancy creams). First line of treatment would be getting a comprehensive test for allergies (both inhalant and food tests). Improving life style may benefit your health as well – try to reduce your stress, sleep more and take the necessary vitamins and supplements. The lack of nutrients ( e.g.Vitamin C, Iron, Vitamin K, Folic Acid) in the diet, or the lack of a balance diet, can contribute to the discoloration of the area under the eyes. Vitamins C & K strengthen the capillary walls and blood vessel walls. Avoid caffeine, sugar-rich drinks and alcohol. Drink plenty of water; at least eight glasses a day. Regular exercise is always helpful, Cold water will cause blood vessels to constrict and reduce swelling.