Dark circles under the eyes or periorbital dark circles, as they’re referred to in medicine, are a sign of fatigue. Some people, however, have these dark circles despite having a good night’s sleep — that’s simply the way they are, and not a cause for concern if it’s hereditary. These periorbital dark circles are very conspicuous because the skin around the eyes is the thinnest in all the body, around four times thinner than the rest of the body to be more precise. Since the skin can become so thin, blood vessels are easily seen. This is why a bruise around the eyes shows worse than any other place on the body — you can just see more easily the ruptured blood vessels through the thin skin. It’s the blood that makes dark circles appear blue, most of the time. Even though blood isn’t blue, the skin only allows violet wavelengths of light to pass through, so only blue light is reflected back to hit retinas, making veins look bluish. People with darker skin tend to have veins which appear green or brown. As an oddity, people with very light skin, such as albinos, will have dark circles that appear dark red or dark purple, which more closely resembles the color of blood. As we age, skin becomes thinner all over the body and loses elasticity, areas around the eyes included. This is why the elderly have prominent periorbital dark circles, even though they’re well rested. Jokingly or not, many say about the elderly that they’ve become tired by living such a long life, which is true to a certain extent but not in the way they think. Some people are genetically predisposed to have dark circles all the time, young or old, because of a condition known as periorbital hyperpigmentation. The condition causes the skin below the eyes to produce more melanin — the pigment that gives human skin, hair, and eyes their color — resulting in it appearing darker. Periorbital hyperpigmentation doesn’t pose any medical risks, “however the development of dark circles under the eyes in any age is of great aesthetic concern because it may depict the individual as sad, tired, stressed, and old,” wrote dermatologist Roberts WE. He says the condition (which mostly affects people with darker skin) is challenging to treat, complex in pathogenesis, and lacking straightforward and repeatable therapeutic options, which is why many turn to cosmetics to cover up the skin around the eyes. Other conditions that may cause dark circles: Allergies Nasal congestion Medical conditions (eczema, thyroid problems, etc.) Venous congestion in under eye blood vessels Environmental exposure Heredity Lifestyle choices can also lead to prominent dark circles around the eyes. These may include: Smoking Hyperpigmentation caused by sun damage Caffeine consumption Alcohol consumption Sleep deprivation Dehydration Dietary deficiencies Bilateral periorbital ecchymosis (raccoon eyes). Raccoon eyes Hand in hand with preorbital dark circles is periorbital puffiness, or saggy bags below the eyes. Allergies, excessive salt consumption, and diseases like the flu cause fluid to build up below the eyes. The saggy bags exert more pressure on the skin and blood vessels which surround the eyes making dark circles appear even more prominent. That’s for young people. As with dark circles, many old people get periorbital puffiness no matter what. Nothing comes close, however, to periorbital ecchymosis, also known as “raccoon eyes” or “panda eyes”. This condition typically occurs when a person suffers a nasty blow to the head, and the resulting skull fracture or ruptured meninges causes blood to flood the soft tissue around the eyes. Sometimes cancer may be involved. Raccoon eyes are serious business and require urgent medical attention which often leads to surgery. Source
