There are a number of reasons why we develop dark circles under the eyes and some are easier to treat than others. The skin around the eyes is thinner than anywhere else on the body, so any problems on the inside show up on the outside. Too many late nights, stress and poor diet can all contribute to shadows around the eyes but genetics also play a part.
If you have an iron deficiency this can cause darkness under the eyes as haemoglobin (the red pigment which carries oxygen to cells) is more easily broken down and this shows up as blue or purple toned darkness under the eyes. Broken capillaries under the skin can also show up as dark circles and these are often caused by too much sun exposure. Brightening and corrective eye creams work best to hide and improve the look of darkness under the eyes, so look for ones that contain Vitamin K Oxide.