Dark circles under the eyes are rarely a sign of illness. They’re one of the most common cosmetic concerns people have, affecting an estimated 30% of adults in some populations, with the majority being women between 16 and 25. The real answer to what causes them is surprisingly layered: it’s almost never just one thing. Most people have a combination of factors working together, which is why dark circles can be so stubbornly persistent.
Why Under-Eye Skin Shows Everything
The skin under your eyes is the thinnest on your entire body. Measurements of facial skin thickness show the eyelid area is roughly 800 microns thick, less than a millimeter. Compare that to the thickest facial skin along the nose, which is about 2,000 microns. This extreme thinness means the under-eye area is essentially translucent. Blood vessels, muscle, and bone sit just beneath the surface with very little tissue to hide them.
That anatomy is the foundation of every cause on this list. Whatever is happening underneath, whether it’s dilated blood vessels, excess pigment, or lost volume, shows through more visibly here than anywhere else on your face.
The Four Types of Dark Circles
Dermatologists classify dark circles into four categories based on what’s actually creating the discoloration. Understanding which type you have matters because each one looks slightly different and responds to different approaches.
Vascular dark circles appear blue, purple, or pink. They’re caused by blood vessels that are dilated or more visible through the thin skin. About 14% of people with dark circles have this as their sole cause.
Pigmented dark circles look brown and result from excess melanin deposited in the skin. This type accounts for roughly 5% of cases on its own.
Structural dark circles are shadows cast by the natural contours of your face, particularly hollows or puffiness. Only about 3% of people have purely structural dark circles. You can identify this type with a simple test: if you gently stretch the skin and the darkness disappears, it’s a shadow, not a color change.
Mixed dark circles combine two or all three of the above. This is by far the most common type, accounting for 78% of cases. If your dark circles seem to change color in different lighting or resist every remedy you try, you’re likely dealing with a combination.
Sleep, Stress, and Blood Vessel Changes
The classic explanation, that dark circles come from not sleeping enough, is real but more nuanced than most people think. The skin around your eyes sits over a dense network of capillaries. When you’re sleep-deprived, stressed, or fatigued, those capillaries dilate and can even break beneath this fragile skin, creating visible areas of discoloration. The effect is similar to a very mild bruise.
Sleep deprivation also causes fluid to pool in the tissues around your eyes, especially the lower lids. This puffiness creates shadows that add to the dark appearance. Sleeping with your head slightly elevated can reduce this fluid buildup. But here’s the part that surprises many people: you can get plenty of sleep and still have dark circles. Sleep is just one of many triggers for vascular changes in this area, and it often combines with genetic or structural factors that no amount of rest will fix.
Allergies and Nasal Congestion
Allergies are one of the most underrecognized causes of dark circles, especially in younger people. The mechanism is straightforward. When your immune system reacts to an allergen, the lining of your nasal passages swells. That swelling slows blood flow in the veins around your sinuses, and those veins run very close to the surface of the skin under your eyes. When they become congested and swollen, the area looks darker and puffy.
This is so common it has its own name: allergic shiners. They tend to look bluish-purple and worsen during allergy season or in dusty environments. Chronic sinus congestion from any cause, not just allergies, can produce the same effect. If your dark circles are worse in spring or fall, or if you also deal with a stuffy nose, this is worth considering.
Excess Pigment From Sun and Skin Irritation
Some dark circles aren’t caused by blood vessels showing through at all. They come from actual pigment buildup in the skin. Melanin, the pigment that gives skin its color, can accumulate under the eyes in response to several triggers: sun exposure, eczema or other forms of dermatitis around the eyes, contact allergies (often from cosmetics or skincare products), and habitual rubbing or scratching.
This type of discoloration is more common in people with darker skin tones. Studies confirm that periorbital darkening has a higher prevalence in darker skin types, where melanin-producing cells are more active and more responsive to inflammation. Any irritation or friction in the area can trigger a cycle of inflammation followed by pigment deposits, a process called post-inflammatory hyperpigmentation. Even something as routine as rubbing your eyes when tired can, over months and years, darken the skin noticeably.
Aging and Volume Loss
As you age, the fat pads that cushion the area around your eyes gradually shrink and shift. At the same time, collagen breaks down, the skin gets even thinner, and the cheek descends slightly. The result is a hollowed groove called the tear trough, the depression that runs from the inner corner of the eye down toward the cheek.
This hollow catches shadows, making the area look dark even when there’s no actual pigment change or vascular issue. Meanwhile, the fat behind the eye socket can push forward, creating puffiness above the hollow that makes the shadow more dramatic. These structural changes typically become noticeable in your mid-30s to 40s and progress with time. People with naturally deep-set eyes or prominent bone structure may notice them earlier.
Iron Deficiency and Reduced Oxygen
When your body doesn’t have enough iron, your red blood cells carry less oxygen. The skin under your eyes, already thin and translucent, can take on a darker or more pallid appearance because the blood flowing beneath it is less oxygenated. The tiny blood vessels become more visible as a result. This is one of the few causes of dark circles that points to an underlying health issue worth addressing, particularly if you also experience fatigue, shortness of breath, or pale skin elsewhere on your body.
Smoking produces a similar effect through a different pathway. It reduces blood oxygen levels and slows circulation, which darkens the appearance of the under-eye area over time.
Diet, Salt, and Fluid Retention
A high-sodium diet causes your body to retain water, and that retained fluid tends to collect in loose tissues like those around the eyes. The resulting puffiness creates shadows and makes existing dark circles look worse. Processed and pre-packaged foods are the biggest sources of hidden sodium for most people. Dehydration, somewhat counterintuitively, can also cause the blood vessels under your eyes to swell, contributing to both puffiness and darkening.
Alcohol has a compounding effect: it dehydrates you while also disrupting sleep quality, hitting two causes at once. If your dark circles are noticeably worse the morning after a salty meal or a night of drinking, fluid retention is likely playing a role.
Genetics and Skin Tone
For many people, the most honest answer is simply genetics. The depth of your eye sockets, the thickness of your skin, the density of blood vessels beneath it, and how readily your body produces melanin in that area are all inherited traits. If your parents had dark circles, your chances are higher regardless of how well you sleep or how carefully you eat. Some families carry a pattern of periorbital pigmentation that appears in childhood and persists throughout life, entirely independent of lifestyle factors.
This genetic component is one reason dark circles can be so frustrating. You can address every modifiable cause, sleep more, manage allergies, wear sunscreen, reduce salt, and still have visible darkness simply because of the way your face is built. In those cases, the darkness isn’t damage or dysfunction. It’s anatomy.