Dark circles under or around your eyes are caused by leaky capillaries, according to Darkcircles.net. Eye circles are comparable to a bruise. When hemoglobin is broken down, what remains is a blue-black color, which is what you are seeing. If, for example, you are hit in the eye, this traumatizes blood vessels. Blood leaks out and permeates the surrounding area and this is where the discoloration occurs. However, some people have dark circles without physical trauma being done to the area around the eye. Some of this is due to genetics but other factors can play a role in creating dark circles.
Medication, Vitamin K Deficiency, Dehydration
Certain medications can make the area around your eye look dark. The medicines that are most likely to cause dark circles are those that dilate blood vessels, according to Docshop.com. Dark circles can develop if you are dehydrated or if you are deficient in vitamin K.
If you are an allergy sufferer, you are apt to develop dark circles. In fact, dark circles are considered one of the symptoms of allergies. Dark smudges will appear around your eyes due to histamine reactions. Furthermore, if you are suffering from allergies you may be rubbing and digging at and around your eyes which will further exacerbate the dark circles.
Swelling and Fatigue
Swelling (edema) may occur if you are suffering from allergies and this will prompt the development of dark circles. Fatigue can also result in dark circles. Being tired doesn't necessarily cause the dark circles; however, if your skin is paler than normal because of fatigue and you are not feeling well, the dark smudges will show up more than they normally do, according to Darkcircles.net.
Dark circles around the eye can be an indication that you have a circulatory problem or kidney or liver malfunction, according to Docshop.com.
Age and Thinning Skin
As we age, our skin doesn't possess as much fat and collagen as it once did. Our skin actually becomes thinner. These factors combined make the blood vessels under our eyes more apparent, according to the Mayo Clinic. Anyone can get dark circles, but they may be more apparent on an older person.
If your nose is stopped up from a cold or sinus infection, this can make dark circles more noticeable. The veins that drain for your eyeballs down to your nose become dilated and darken when congestion occurs.
Too Much Sun
The more sun you get, the more pronounced your dark circles are going to be. Sun exposure increases the production of pigment (melanin) in the skin and makes the dark circles even darker.