Dark circles under your eyes usually come down to one of four things: visible blood vessels, excess pigment in the skin, a shadow cast by lost volume beneath the eye, or some combination of all three. The skin under your eyes is the thinnest on your entire body, which means anything happening just beneath the surface shows through more easily than it would anywhere else on your face.
Most people assume dark circles are simply a sign of not sleeping enough. Sleep deprivation can make them worse, but the underlying causes are more varied and often more stubborn than a single bad night.
Why the Under-Eye Area Is So Vulnerable
The skin covering your eyelids and the area just below your eyes is thinner than skin anywhere else on your body. It contains very little subcutaneous fat, so the blood vessels, muscle, and bone underneath are closer to the surface. On the rest of your face, thicker skin with more fat padding obscures what’s going on beneath. Under your eyes, that padding barely exists, and the result is a translucent window that reveals color changes, fluid shifts, and structural changes more readily.
This is why dark circles can look dramatically different from one morning to the next. A night of poor sleep, a salty meal, or a bout of seasonal allergies can all shift the appearance of this area within hours, precisely because there’s so little tissue acting as a buffer.
Blood Vessels Showing Through Thin Skin
The most common type of dark circle has a bluish or purplish tint and is caused by blood vessels visible through that thin skin. When blood pools in the small veins beneath your eyes, the area takes on a darker hue. This is especially noticeable in people with naturally fair or thin skin, and it tends to worsen with fatigue because sleep deprivation dilates blood vessels and increases blood flow to the area.
Aging amplifies this effect. As you get older, you lose collagen and fat in the under-eye area, making skin that was already thin even more transparent. The veins that were always there become progressively easier to see.
Allergies and Nasal Congestion
If your dark circles get worse during allergy season, the connection is direct and physical. When your immune system reacts to an allergen, the moist lining inside your nose swells. That swelling slows blood flow in the veins around your sinuses, and those veins run close to the surface just beneath your eyes. When blood backs up and pools there, the area looks darker and puffier. Doctors sometimes call these “allergic shiners.”
This isn’t limited to seasonal allergies. Chronic sinus congestion from colds, dust mite sensitivity, or pet dander can produce the same effect year-round. Anything that keeps your nasal passages swollen restricts the drainage of blood from the under-eye veins, and the discoloration follows.
Excess Melanin in the Skin
Some dark circles aren’t caused by blood vessels at all. They’re caused by the skin itself being darker in the under-eye area due to higher concentrations of melanin. This type of dark circle tends to look brown rather than blue or purple and is more common in people with deeper skin tones.
Genetics play a significant role here. Researchers have identified specific gene variations linked to pigment-related dark circles, including changes in genes that regulate both pigment production and blood vessel growth. Sun exposure worsens pigmentation-based dark circles because UV light triggers more melanin production in skin that’s already prone to it. Rubbing your eyes frequently, whether from allergies or habit, can also darken the skin over time through repeated friction and inflammation.
Volume Loss and Shadows
Not all dark circles involve color changes in the skin at all. Some are optical illusions created by the shape of your face. The “tear trough” is the groove that runs from the inner corner of your eye down along your cheekbone. In younger faces, fat pads fill this area and create a smooth transition between the lower eyelid and the cheek. With age, that fat shrinks and the surrounding tissue descends, deepening the groove and creating a hollow.
The depression casts a shadow, and the shadow looks like a dark circle. This type is most obvious in overhead lighting and tends to worsen gradually through your 30s and 40s. The central portion of the ligament holding the fat pad in place is the weakest point, so it stretches and sags first, which is why the hollowing often appears most prominently in the middle of the under-eye area before spreading outward.
Lifestyle Factors That Make It Worse
Several everyday habits can intensify dark circles regardless of their root cause.
A high-salt diet causes your body to retain fluid, and that extra fluid tends to accumulate in loose tissue like the area under your eyes. The result is puffiness that casts additional shadows and makes vascular dark circles more prominent. Alcohol has a similar effect through dehydration: when you’re dehydrated, your body compensates by holding onto water, and the under-eye area swells. Drinking more water and reducing salt intake can visibly reduce this type of fluid buildup.
Sleep deprivation doesn’t cause dark circles on its own, but it makes every other cause worse. Fatigue dilates blood vessels (making vascular circles more visible), promotes fluid retention (adding puffiness), and makes skin look paler overall (increasing the contrast between your under-eye area and the rest of your face). Screen time before bed compounds the problem by disrupting sleep quality and causing eye strain that increases blood flow to the area.
How to Tell Which Type You Have
A simple test can help you figure out whether your dark circles are caused by pigment, blood vessels, or shadows. Gently pinch and lift the skin beneath your eye. If the dark color lifts with the skin, pigmentation is likely the main cause. If the color disappears when you stretch the skin, you’re probably seeing blood pooling beneath it, thinned skin, or shadows from volume loss underneath.
Color is another clue. Bluish or purple tones point to visible blood vessels. Brown or tan tones suggest melanin. A hollow or indentation that looks worse in certain lighting suggests a structural shadow. Many people have a combination, which is why dark circles can be frustratingly difficult to treat with a single approach.
What Actually Helps
Because the causes differ, treatments that work for one type of dark circle may do nothing for another.
For vascular dark circles, cold compresses constrict blood vessels temporarily and reduce the blue-purple appearance. Caffeine-containing eye creams are widely marketed for this purpose, but research suggests the cooling sensation of the product may matter more than the caffeine itself. One study found that a caffeine gel reduced puffiness better than a plain gel base in only about 24% of volunteers, suggesting that individual responses vary widely and that the cold temperature of the product does most of the work.
For pigmentation-based circles, sun protection is the most effective preventive measure. Sunscreen applied to the under-eye area, along with sunglasses, slows further melanin buildup. Topical products containing vitamin C or other brightening agents can gradually lighten excess pigment, though results take weeks to months.
For shadow-based circles caused by volume loss, topical products have limited impact because the problem is structural. Dermal fillers injected into the tear trough can restore volume and smooth the transition between the lower eyelid and cheek, reducing the shadow. Results typically last six months to a year.
For allergy-related circles, treating the underlying congestion is the most direct solution. When nasal swelling goes down, blood flow through the under-eye veins normalizes and the discoloration fades. Antihistamines and nasal sprays address the root cause in a way that concealer never will.
Regardless of the type, adequate sleep, hydration, and moderate salt intake form a baseline that prevents dark circles from looking worse than they need to. These won’t eliminate genetic or age-related causes, but they remove the lifestyle factors that amplify them.