Under Eye Circles.

Dark circles under your eyes can be caused by an abundance of different factors and most of the time it is not due to lack of sleep or one too many drinks the night before. Illness, allergies, genetics, gluten intolerance, hyperpigmentation etc. can all contribute to raccoon eyes.

Unfortunately there is no magic cure for this issue but there are tricks that can help mask the look of them:

Apply refrigerated witch hazel to a cotton pad and let it sit under your eyes for approximately 10 minutes.

You can also slightly steep two teabags in warm water and apply to your eyes (keep them closed) for about 10 - 15 minutes. The caffeine and tannin in the tea itself will help reduce any swelling and discolouration.

My final suggestion is makeup! It seems like an easy fix but sometimes applying makeup to under eye circles can make them appear darker. The truth is that there is no way to completely hide under eye circles with makeup but it is possible to make them appear less prominent.
When choosing what product to use it is best to keep the formula light in texture. If your concealer is too thick it will begin to look cakey and synthetic.
Apply a thin layer of concealer using a brush (avoid using your fingers as the heat and oils produced by them will break down the product). Once you have finished applying the concealer, set it with a translucent powder - this will help stop creasing half way through the day.

A few products that are great for under the eyes are Amazing Cosmetics Amazing Concealer (found at Sephora), MAC Fast Response Eye Cream and MAC Select Moisturecover.