Dark circles under the eyes rarely have a single cause. They result from a combination of factors, including thin skin, visible blood vessels, loss of facial fat, excess pigment, and sometimes allergies or nutritional deficiencies. Understanding which type you have matters because the underlying mechanism determines whether anything can actually improve them.
Why the Under-Eye Area Is So Vulnerable
The skin beneath your eyes is some of the thinnest on your body, roughly 0.5 mm compared to about 2 mm elsewhere on the face. That thinness means blood vessels, muscle, and bone sit closer to the surface, making any changes in color, volume, or blood flow immediately visible. On thicker skin, you’d never notice these same changes.
This also explains why dark circles can seem to appear overnight after poor sleep or a long cry. The underlying structures haven’t changed, but temporary fluid shifts or blood vessel dilation make them more apparent through that paper-thin skin.
The Four Main Types of Dark Circles
Vascular (Bluish or Purple)
If your dark circles look blue, purple, or reddish, the cause is almost always visible blood vessels beneath the skin. Blood pooling in the tiny veins under the eye creates a bluish tint that shows through the translucent skin. This type is more noticeable in people with fair or thin skin and tends to worsen with fatigue, since sleep deprivation dilates blood vessels. Pressing gently on the area and watching it briefly lighten, then darken again, is a hallmark of vascular dark circles.
Pigmented (Brown)
Brown or brownish-gray dark circles come from excess melanin in the skin itself. Histological studies show melanin pigment accumulating within cells in the upper layer of the dermis around the eyes. This type is more common in people with darker skin tones and often runs in families. Sun exposure accelerates it because UV radiation triggers more melanin production in an area that’s already prone to pigmentation. Hormonal changes during puberty and pregnancy can also trigger or worsen pigmented dark circles, as can recovery from certain acute illnesses.
Structural (Shadow-Based)
Some dark circles aren’t caused by color at all. They’re shadows. A deep groove between the lower eyelid and the cheek, called the tear trough, creates a shadow that looks like a dark circle in most lighting conditions. Puffy lower eyelids or under-eye bags make this worse by creating a visible ridge that casts its own shadow below it. If your dark circles seem to disappear in certain lighting or photographs taken with a flash, the structural shadow effect is likely a major contributor.
Mixed
Most people have a combination of two or three of these types happening simultaneously. A person might have naturally thin skin (vascular component), mild pigmentation from sun exposure, and early volume loss creating a slight shadow. This overlap is one reason dark circles are so stubborn to treat.
How Aging Makes Dark Circles Worse
Age-related changes hit the under-eye area hard from multiple directions at once. The fat pad that sits beneath the eye socket shrinks and shifts downward over time, deepening the tear trough and making shadows more pronounced. The supporting ligaments weaken, allowing remaining fat to bulge forward as under-eye bags while the area below hollows out. Meanwhile, the underlying bone gradually resorbs, which removes structural support and deepens the hollow even further.
On top of the volume loss, the skin itself loses collagen and becomes thinner and more translucent with each decade, making blood vessels increasingly visible. This is why many people notice dark circles worsening steadily in their 30s and 40s even if they sleep well and stay hydrated.
Allergies and Sinus Congestion
The dark, puffy look sometimes called “allergic shiners” has a specific mechanism. When your immune system reacts to allergens, the moist lining inside your nose swells. That swelling slows blood flow through the veins around the sinus cavities, and those veins happen to run close to the surface right under your eyes. When they swell with backed-up blood, the area looks darker and puffier.
This isn’t limited to seasonal allergies. Chronic sinus congestion from any cause, including dust mite sensitivity or pet dander exposure, can produce the same effect. People with asthma, eczema, or atopic dermatitis also have higher rates of periorbital darkening, likely because of the same underlying inflammatory pathways.
Genetics and Skin Tone
Family history is one of the strongest predictors of dark circles. If your parents had them, you probably will too, regardless of how much sleep you get. Genetics influence skin thickness, the density of blood vessels beneath the eyes, the depth of the tear trough, and how readily your skin produces melanin in the periorbital area.
People with deeper skin tones are more prone to the pigmented type, while people with very fair or translucent skin are more prone to the vascular type. Neither is more “severe,” but they respond to different approaches. This genetic component is also why dark circles often appear in childhood or adolescence, long before aging plays any role.
Sleep, Anemia, and Other Contributing Factors
Sleep deprivation doesn’t cause dark circles on its own, but it amplifies them. Poor sleep dilates blood vessels, increases fluid retention, and makes skin look paler, all of which make existing under-eye darkness more visible. The same goes for dehydration and alcohol consumption.
Iron deficiency anemia can contribute to dark circles through a different mechanism. When you don’t have enough healthy red blood cells carrying oxygen, the blood flowing through those visible under-eye veins is less oxygenated, giving it a darker, more bluish appearance. Anemia-related dark circles often come with other symptoms like fatigue, pale skin, and shortness of breath.
Frequent eye rubbing, whether from allergies, habit, or eczema, causes mechanical trauma to the delicate under-eye skin. Over time, this repeated friction stimulates melanin production and can damage tiny blood vessels, worsening both pigmented and vascular dark circles. Sun exposure without eye protection does something similar, accelerating pigment deposition in skin that’s already thin and vulnerable.
How to Tell Which Type You Have
A simple stretch test can help. Gently pull the skin under your eye taut and look in a mirror. If the color improves, you likely have a vascular component, since stretching the skin moves blood vessels slightly away from the surface. If the color stays the same or looks worse, excess pigment is more likely the cause. If the darkness disappears entirely under direct, flat lighting (like a ring light), the issue is primarily structural shadowing.
The color itself is also a clue. Blue or purple points to blood vessels. Brown or dark gray suggests melanin. A hollow or indentation you can feel with your fingertip indicates volume loss. Most people will find they check more than one box, which is normal and expected given the multifactorial nature of under-eye darkening.