Dark circles under your eyes are caused by a combination of unusually thin skin, visible blood vessels, excess pigment, and age-related volume loss. Most people have more than one of these factors at play, which is why dark circles can be so stubborn. Understanding which type you’re dealing with is the first step toward addressing them effectively.
Why Under-Eye Skin Shows Everything
The skin beneath your eyes is some of the thinnest on your entire body. A high-frequency ultrasound study measuring facial skin thickness found that the upper eyelid has a median thickness of just 0.57 mm, while the lower eyelid measures about 0.81 mm. Compare that to the thickest facial skin, at the tip of the nose, which comes in at nearly 1.91 mm. That’s more than double the thickness of your lower eyelid.
This thinness matters because it makes the underlying structures, especially blood vessels and muscle, far more visible. The bluish or purplish tint many people notice under their eyes isn’t a stain on the skin itself. It’s the color of blood flowing through tiny veins just beneath the surface. Anything that makes those vessels swell or the skin even slightly thinner will intensify the appearance of dark circles.
Genetics and Family History
If your dark circles showed up in childhood and your parents have them too, genetics is likely the primary driver. Researchers have documented families in which dark under-eye pigmentation appeared across six generations, affecting 22 members of a single family. Some individuals were mildly affected, others severely, but the pattern was consistent: the circles appeared early in life and deepened with age.
Genetic dark circles can involve either extra pigment in the skin or naturally thinner skin that lets vessels show through more prominently. People with deeper skin tones are more prone to the pigment-driven type, while those with lighter, more translucent skin tend to see the vascular version. In both cases, the trait is inherited and not a sign of illness or poor health habits.
Blood Vessel Visibility and Congestion
Vascular dark circles look blue, purple, or sometimes reddish. They result from blood pooling in the small veins beneath the under-eye skin. Several things can make this worse.
Allergies are one of the most common culprits. 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 sit close to the surface of the skin under your eyes. When those veins become congested and swell, the area looks darker and puffier. This phenomenon, sometimes called “allergic shiners,” is especially common in people with chronic nasal allergies or frequent sinus congestion.
Sleep deprivation works through a similar mechanism. When you’re tired, blood vessels dilate, and the skin can appear paler, making the contrast between the under-eye area and the rest of your face more dramatic. Fluid can also accumulate overnight if you sleep flat, adding puffiness that casts its own shadow.
Excess Melanin Production
Some dark circles are caused by the skin itself producing too much pigment. These tend to look brown or dark brown rather than blue or purple, and they’re more common in people with medium to dark skin tones.
UV exposure is a direct trigger. Ultraviolet radiation stimulates pigment-producing cells in the skin, and because under-eye skin is so thin, even modest sun exposure can darken the area noticeably. Wearing sunscreen and sunglasses helps slow this process.
Inflammation is another pathway. Conditions like eczema and allergic contact dermatitis can leave behind excess pigment after the irritation itself resolves. This post-inflammatory darkening is common around the eyes because people tend to rub itchy eyes, and that repeated friction triggers more pigment production. Certain medications can also cause localized darkening in the same area. Hormonal changes during pregnancy have been linked to increased pigmentation around the eyes as well.
Volume Loss and Tear Troughs
Not all dark circles are actually dark. Some are shadows cast by hollows beneath the eye, a structural issue that becomes more common with age. The groove that runs from the inner corner of the eye down toward the cheek is called the tear trough. In younger faces, a pad of fat fills this area and creates a smooth transition between the lower eyelid and the cheek.
As you age, that fat pad shrinks. The bone beneath it also loses volume. Meanwhile, the skin and muscle above it become laxer and thinner. The result is a deepening groove that creates a shadow, which reads as a dark circle even though the skin color itself hasn’t changed. This is why some people find that concealer doesn’t fully solve the problem: you can’t cover a shadow the same way you cover pigment. Midface descent, where the cheek gradually drops, further deepens the tear trough over time.
Anemia and Iron Deficiency
Low iron levels can make dark circles more noticeable through two mechanisms. First, when hemoglobin drops, your skin becomes paler overall. That pallor increases the contrast between the rest of your face and the naturally darker under-eye area. Second, with insufficient hemoglobin carrying oxygen through your blood, the tissue around the eyes can become slightly oxygen-deprived, which gives the area a darker, more congested appearance.
Anemia alone rarely causes dark circles from scratch, but it can make existing circles look significantly worse. If your dark circles appeared or worsened alongside fatigue, shortness of breath, or unusually pale skin, an iron panel can rule this out.
Why Most People Have More Than One Cause
Dark circles are rarely explained by a single factor. Someone might have genetically thin skin (vascular component), live in a sunny climate (pigment component), and be in their 40s (volume loss component), all compounding at once. This is why treatments that target only one mechanism often produce underwhelming results.
The color of your circles offers a useful clue. Blue or purple tones point to visible blood vessels. Brown or dark brown suggests excess pigment. A hollow or indentation that looks worse in certain lighting is likely structural volume loss. Many people have a mix.
What Actually Helps
Topical treatments work best for vascular and pigment-driven circles. Caffeine applied topically at concentrations up to 3% constricts blood vessels and has been shown to reduce under-eye pigmentation and improve skin brightness in clinical testing. Niacinamide at 5% can help with pigmentation when used consistently over 12 weeks. Sunscreen applied daily to the under-eye area slows UV-driven pigment accumulation.
For structural dark circles caused by volume loss, topical products have limited effect because the issue is beneath the skin rather than within it. Dermal fillers injected into the tear trough can restore lost volume and eliminate the shadow, though results are temporary and need to be repeated. Cold compresses and sleeping with your head slightly elevated can reduce the morning puffiness that worsens shadows.
Managing allergies with antihistamines reduces vascular congestion and can visibly lighten allergic shiners within days. If you notice your dark circles worsen during allergy season, that’s a strong signal that sinus congestion is a major contributor for you.