Dark circles under the eyes are almost always caused by some combination of thin skin, visible blood vessels, excess pigment, or shadows cast by lost volume. In a clinical study of 65 people with under-eye darkness, 78% had a mix of these factors rather than a single cause, which explains why dark circles can be so stubborn and hard to treat with one approach.
Why the Under-Eye Area Shows Everything
The skin beneath your eyes is the thinnest on your entire face. High-frequency ultrasound measurements show the upper eyelid has a median thickness of just 573 micrometers, roughly half a millimeter. The lower eyelid is slightly thicker at around 800 micrometers but still far thinner than other facial skin. The thickest skin on the face, at the tip of the nose, is more than three times as thick as the lower eyelid.
This matters because thinner skin is more translucent. Blood vessels, muscle, and bone sit closer to the surface, and any changes in blood flow, pigmentation, or tissue volume become immediately visible. Think of it like wearing a white T-shirt versus a thick sweater: the same things are underneath, but one lets everything show through.
The Four Types of Dark Circles
Clinicians generally sort under-eye darkness into four categories based on what’s driving the discoloration. Understanding which type you have changes what (if anything) will actually help.
- Vascular (blue, pink, or purple): Blood vessels beneath the thin skin show through, creating a bluish or purplish tint. This type looks worse when you’re tired, dehydrated, or congested because those conditions dilate blood vessels or slow blood flow.
- Pigmented (brown): Excess melanin deposits in the skin itself create a brownish discoloration. This is more common in people with darker skin tones and can be genetic or triggered by sun exposure and inflammation.
- Structural (shadow-based): The darkness is actually a shadow created by the contour of your face, often from a deep groove (tear trough) or puffy fat pads above it. A quick test: if you gently stretch the skin and the darkness disappears, it’s a shadow, not pigment or veins.
- Mixed: The most common type by far. In one classification study, only 5% of cases were purely pigmented, 14% purely vascular, and 3% purely structural. The remaining 78% were some combination.
Genetics and Skin Tone
Some people are simply born with darker pigmentation around the eyes. This is called constitutional pigmentation, and it runs in families. It’s especially common in people of South Asian, Southeast Asian, Middle Eastern, and African descent, though it occurs across all skin tones. If your parents or siblings have prominent dark circles that have been present since childhood, genetics is likely the primary factor.
People with naturally fair or translucent skin, on the other hand, are more prone to the vascular type. Their skin doesn’t have more blood vessels than anyone else’s, but the lack of melanin in the overlying skin makes those vessels much more visible.
Aging and Volume Loss
Dark circles often worsen with age even if you sleep well and stay hydrated. Several things change simultaneously. The fat pads that cushion the area beneath the eye shrink and shift downward. The ligaments connecting skin to bone loosen, especially in the central portion of the under-eye area, which is the weakest point. And the skin itself loses collagen, becoming even thinner and more translucent.
These changes create what’s known as the tear trough, a hollow groove running from the inner corner of the eye toward the cheek. Because the skin in this area has very little subcutaneous fat to begin with, even modest volume loss creates a noticeable depression. That depression casts a shadow, making the area look dark regardless of your actual skin color or vein visibility. People with a more prominent cheekbone can develop a deeper tear trough because the gap between bone and skin in this region is larger.
Sleep, Fatigue, and Dehydration
Poor sleep doesn’t cause dark circles from scratch, but it makes existing darkness more obvious. When you’re tired, your body produces more cortisol to keep you alert, which increases blood volume and dilates blood vessels. The tiny veins beneath your under-eye skin engorge and become more visible through the translucent skin above them. Dehydration has a similar effect: when your body is low on water, the skin looks duller and more sunken, exaggerating shadows and making veins more prominent.
This is why a bad night’s sleep can make your dark circles look dramatically worse even though nothing structural has changed. It’s also why cold compresses offer temporary relief. Cold temperatures constrict those dilated blood vessels, reducing the bluish tint for a short period.
Allergies and Sinus Congestion
The dark, puffy discoloration that appears during allergy season has its own name: allergic shiners. When your immune system reacts to an allergen, the lining inside your nose swells. That swelling slows blood flow through the veins around your sinuses, and those veins happen to run just beneath the surface of the under-eye skin. As blood pools and the veins expand, the area looks darker and puffier.
Allergies also cause itching, and repeated rubbing of the eye area creates a second problem. Physical friction triggers the skin’s melanocytes (pigment-producing cells) to ramp up melanin production. This post-inflammatory hyperpigmentation can outlast the allergy season itself, leaving behind brownish discoloration that takes weeks or months to fade. The same mechanism applies to eczema around the eyes or any chronic irritation in the area.
Iron Deficiency and Anemia
When your body doesn’t have enough iron, your blood carries less oxygen. The skin under your eyes, already thin and poorly cushioned, becomes paler from reduced blood flow. Paradoxically, this makes the underlying blood vessels stand out more against the lighter background. The result looks similar to vascular dark circles from fatigue but doesn’t improve with better sleep.
Iron deficiency is worth considering if your dark circles appeared or worsened alongside other symptoms like unusual fatigue, shortness of breath during normal activity, or pale skin on your inner eyelids and nail beds. A simple blood test can confirm or rule it out.
Sun Exposure and Inflammation
UV radiation stimulates melanin production everywhere on the face, but the under-eye area is disproportionately affected because the skin there is so thin and delicate. Years of sun exposure without protection gradually darkens the periorbital area relative to surrounding skin.
Any inflammatory skin condition in the eye area, including contact dermatitis from makeup or skincare products, eczema, or repeated waxing, can also leave behind post-inflammatory hyperpigmentation. The process is straightforward: inflammation damages the outer layer of skin, which signals melanocytes to produce extra pigment. That pigment can deposit both in the surface layers and deeper in the skin. When melanin settles in the deeper layers, the discoloration takes longer to resolve, sometimes persisting for months after the original irritation has cleared.
What Actually Helps
Because most dark circles involve multiple causes, effective treatment usually means addressing more than one factor. Vascular dark circles respond to anything that constricts blood vessels: cold compresses, caffeine-containing eye creams, and adequate sleep. These effects are real but temporary, lasting hours rather than days.
For pigmentation-driven darkness, ingredients that interrupt melanin production, such as hydroquinone, kojic acid, and arbutin, can gradually lighten the area over weeks of consistent use. Sunscreen is essential here, since UV exposure will undo any progress. Topical vitamin K may help with visible blood vessels specifically, as it has both vessel-constricting and anti-inflammatory properties.
Vitamin C is one of the few ingredients with clinical evidence for structural improvement. In a six-month trial, a 10% vitamin C product increased the thickness of the under-eye skin, making blood vessels less visible. The mechanism is collagen stimulation: thicker skin means less show-through. This is a slow process, requiring months of daily application, but it addresses one of the root causes rather than just masking the appearance.
Structural dark circles caused by volume loss and tear trough deformity don’t respond well to topical products. The shadow is created by anatomy, not pigment or vessels. Injectable fillers placed along the tear trough can restore lost volume and reduce the shadow effect, though results vary depending on facial bone structure and the degree of fat loss. For allergic shiners, treating the underlying allergy with antihistamines or nasal corticosteroids reduces sinus congestion and allows normal blood flow to resume, which gradually lessens the discoloration.