Dark circles under your eyes form because the skin there is the thinnest on your entire body, making everything beneath it more visible. Blood vessels, bone structure, pigment changes, and fluid buildup all show through this delicate area in ways they wouldn’t anywhere else on your face. Most people have more than one factor contributing at the same time.
Why Under-Eye Skin Is So Revealing
The skin covering your eyelids and the area just below your eyes is significantly thinner than the rest of your facial skin. It has less fat padding underneath and fewer oil glands to keep it plump. This means the tiny blood vessels running just below the surface are closer to the outside world, and their color shows through more easily. When those vessels dilate or blood pools in them, the skin takes on a blue, purple, or pinkish hue that reads as a “dark circle.”
This basic anatomy explains why almost everyone has some degree of under-eye darkness, and why it tends to get worse with age, fatigue, or anything that changes blood flow to the area.
The Four Types of Dark Circles
Not all dark circles look the same or come from the same cause. Dermatologists classify them into four categories based on what’s actually happening beneath the skin.
Vascular dark circles appear blue, pink, or purple. They’re caused by blood vessels showing through thin skin, sometimes with puffiness. About 14% of people with dark circles have a purely vascular type. Pigmented dark circles look brown and come from excess melanin deposited in the skin itself. Only about 5% of cases are purely pigmented. Structural dark circles are actually shadows cast by the natural contours of your face, particularly hollows beneath the eye. These account for roughly 3% of cases on their own. You can test for this type by gently stretching the skin: if the darkness disappears, it’s a shadow, not pigment or blood vessels.
The remaining 78% of people have a mixed type, combining two or three of these factors. This is why dark circles can be so stubborn. You might be dealing with visible blood vessels, extra pigment, and a hollow groove all at once.
How Aging Changes the Under-Eye Area
The “tear trough” is the groove that runs from the inner corner of your eye down along your nose. In younger faces, a layer of fat and firm skin covers this area smoothly. As you age, several things happen simultaneously: the fat pads beneath the skin shrink, the skin itself loses elasticity, and the cheek tissue descends slightly. This uncovers the bony rim of your eye socket and deepens the groove, creating a shadow that wasn’t there before.
At the same time, the fat pads behind your eyeball can push forward (herniate), creating puffiness above the hollow. The contrast between a puffy upper area and a sunken lower area makes the shadow even more dramatic. Bone density in the upper jaw also decreases with age, which can deepen the trough further. These structural changes explain why many people notice dark circles worsening in their 30s and 40s even when their sleep and health haven’t changed.
Allergies and Sinus Congestion
If your dark circles get worse during allergy season, there’s a direct explanation. When your immune system reacts to allergens, the moist lining inside your nose swells. That swelling slows blood flow through the veins around your sinuses, which happen to sit very close to the surface of the skin under your eyes. The backed-up blood makes those veins swell and darken the area, creating what doctors sometimes call “allergic shiners.”
This effect isn’t limited to seasonal allergies. Chronic sinus congestion from dust mites, pet dander, or even frequent colds can produce the same venous pooling. Rubbing itchy eyes compounds the problem by irritating the skin and potentially increasing pigment production over time.
Sleep, Fluid, and Daily Habits
Poor sleep is probably the most commonly blamed cause of dark circles, and there’s a real mechanism behind it. Both too little and too much sleep can trigger fluid retention around the eyes. When fluid builds up in the tissue under your eyes, it creates puffiness and stretches the already-thin skin, making blood vessels beneath even more visible. Sleep deprivation also tends to make skin paler overall, which increases the contrast between your face and the darker under-eye area.
Dehydration works differently but produces a similar result. When you’re dehydrated, the skin loses volume and clings more tightly to the underlying structures, making hollows and blood vessels more apparent. Alcohol and high-sodium diets swing things the other direction, promoting fluid retention and puffiness that casts shadows.
Screen time deserves a mention too. Prolonged staring at screens causes eye strain, which increases blood flow to the muscles around your eyes. That extra blood in the area can darken the appearance of already-thin skin.
Iron Deficiency and Anemia
When your body doesn’t have enough iron, it produces fewer healthy red blood cells, which means less oxygen-rich blood circulating through your system. Oxygen-poor blood is darker in color, and that darker blood flowing through the superficial veins under your eyes can make the area look noticeably more shadowed. The reduced oxygen delivery also makes surrounding skin paler, amplifying the contrast.
That said, dark circles alone are not a reliable sign of anemia. Most people with dark circles are not anemic, and many anemic people don’t develop noticeable under-eye changes. If you have other symptoms like unusual fatigue, shortness of breath, or pale skin elsewhere on your body, iron levels are worth checking. But dark circles in isolation point much more often toward the structural and vascular causes described above.
Genetics and Skin Tone
Genetics is one of the strongest predictors of dark circles. If your parents had them, you’re likely to develop them too, regardless of how well you sleep or how much water you drink. What’s inherited isn’t a single trait but a collection of them: how thin your skin is, how deep your tear trough sits, how much melanin your body deposits around the eyes, and how prominent your blood vessels are.
People with deeper skin tones are more prone to the pigmented type of dark circles because their skin naturally produces more melanin, and the under-eye area can accumulate pigment faster than surrounding skin. People with lighter, more translucent skin tend toward the vascular type, where blue and purple blood vessels show through more readily. Neither type is more or less “normal.” They’re simply different expressions of the same thin-skin anatomy.
Sun Exposure and Pigment Changes
Ultraviolet light stimulates melanin production everywhere on your body, but the effect is particularly noticeable under the eyes because the skin there is so thin and delicate. Repeated sun exposure without protection can gradually darken the under-eye area, especially in people already prone to pigmented dark circles. This type of darkening tends to be brown rather than blue and doesn’t improve much with sleep or hydration changes.
Sunscreen and sunglasses are the most straightforward preventive measures for this specific cause. Once excess pigment has been deposited, it’s harder to reverse than vascular or structural darkening.
What Actually Helps
Because most dark circles involve multiple causes, no single fix works for everyone. Addressing the dominant type matters. Vascular dark circles often improve with cold compresses (which constrict blood vessels), better sleep, and managing allergies or congestion. Pigmented dark circles respond best to sun protection and topical products containing ingredients that slow melanin production, like vitamin C or niacinamide. Structural dark circles, caused by volume loss and hollowing, don’t respond to topical treatments at all. They’re a shadow problem, and the most effective approach is restoring volume beneath the skin through injectable fillers placed along the tear trough.
For the mixed type that most people have, a combination approach works best. Consistent sleep, hydration, allergy management, and sun protection address the controllable factors. Topical products with retinol can thicken the skin slightly over months of use, reducing vascular show-through. And for the structural component that worsens with age, volume restoration remains the most direct solution. Color-correcting concealer, while not a treatment, is the fastest way to neutralize the appearance: peach or orange tones counteract blue-purple darkness, while yellow tones work on brown pigmentation.