Dark circles under your eyes usually come from one of four things: visible blood vessels showing through thin skin, excess pigment production, structural shadows from volume loss, or a combination of all three. Genetics, aging, and lifestyle habits are the most common drivers, though allergies and certain health conditions can play a role too.
Thin Skin and Visible Blood Vessels
The skin under your eyes is some of the thinnest on your entire body. When that skin is especially thin or translucent, the network of tiny blood vessels beneath it shows through, giving the area a blue, purple, or pink tint. Some people are born with naturally thinner skin in this area, which is why dark circles can start in childhood and run in families.
As you age, the skin below your eyes loosens and thins further, making those blood vessels even more visible. This is one reason dark circles tend to get more noticeable in your 30s and beyond, even if your sleep and habits haven’t changed. Fair skin makes vascular dark circles more obvious, but they can appear in any skin tone.
Excess Melanin Production
In many cases, the darkness under your eyes is actual pigment, not just blood vessels showing through. Your body produces more melanin in the under-eye area in response to several triggers. Sun exposure is the biggest one. UV light stimulates pigment-producing cells, and because the skin around your eyes is so delicate, even casual sun exposure can darken it over time. Broad-spectrum sunscreen is considered the single most important preventive step for this type of dark circle.
Rubbing your eyes frequently can also trigger pigment deposits. When skin is irritated or inflamed repeatedly, it responds by producing extra melanin at the site of damage. This process, called post-inflammatory hyperpigmentation, is why people with eczema or chronic allergies around their eyes often develop persistent darkening. People with darker skin tones are more prone to pigment-driven dark circles because their melanocytes (pigment cells) are more reactive to inflammation and UV exposure.
Structural Shadows and Volume Loss
Sometimes the “dark circle” isn’t pigment or blood vessels at all. It’s a shadow. As you age, the fat pads that cushion the area beneath your eyes shift downward and thin out. At the same time, the bone structure of your mid-face gradually loses volume. Together, these changes create a hollow groove between your lower eyelid and your cheek, sometimes called the tear trough.
This depression catches light in a way that casts a shadow, making the area look darker than it actually is. The ligament that anchors soft tissue in this area also weakens with age, allowing it to stretch and deepen the groove further. People with naturally prominent cheekbones or a deep-set bone structure may develop this hollowed look earlier, since there’s a larger gap between the bone and the skin in the tear trough area. If you tilt your head back and the darkness largely disappears, structural shadowing is likely a significant factor for you.
Allergies and Nasal Congestion
If your dark circles worsen during allergy season, there’s a direct physical explanation. When your immune system reacts to allergens, the lining inside your nose swells. That swelling compresses the veins that drain blood from the area around your sinuses, and those veins happen to sit right beneath the skin under your eyes. When blood flow slows in these veins, they swell and darken the area visibly. Doctors sometimes call this effect “allergic shiners.”
The discoloration from allergic shiners tends to look puffy and bluish, and it fluctuates with your congestion. Chronic allergies, sinus infections, or anything that keeps your nasal passages inflamed for weeks at a time can make the darkening persistent. Treating the underlying congestion typically improves the appearance.
Sleep, Dehydration, and Daily Habits
Poor sleep doesn’t cause dark circles on its own, but it makes existing ones worse. When you’re tired, your skin looks paler, which increases the contrast with the blood vessels underneath. Fluid can also pool beneath your eyes overnight, adding puffiness that casts additional shadows. Sleeping with your head slightly elevated on an extra pillow helps prevent that fluid buildup.
Dehydration reduces the water content of the soft tissue around your eyes, making the area look more sunken and hollow. This is one of the most quickly reversible causes. Rehydrating can visibly improve the appearance within a day. Alcohol and caffeine both pull water from this tissue and can worsen the hollowed look over time, especially with regular heavy use.
Anemia and Other Health Conditions
Iron-deficiency anemia can contribute to dark circles because when your blood doesn’t carry enough oxygen, it appears darker as it flows through the tiny vessels under your eyes. The combination of poorly oxygenated blood and thin skin creates a noticeable discoloration. If your dark circles appeared suddenly or are accompanied by fatigue, pale skin, or shortness of breath, low iron levels are worth checking with a blood test.
Thyroid disorders, particularly an underactive thyroid, can also cause puffiness and darkening around the eyes. These medical causes are less common than genetics or aging, but they’re worth considering if your dark circles don’t match any obvious lifestyle explanation.
Treatments That Target the Cause
Because dark circles have different root causes, no single treatment works for everyone. The most effective approach depends on which type you have.
For pigment-driven dark circles, topical treatments that slow melanin production are the standard approach. Vitamin C applied as a serum both inhibits pigment formation and thickens the delicate skin by boosting collagen, which helps conceal underlying blood discoloration. Azelaic acid, available over the counter at lower concentrations, works by reducing melanocyte activity and is especially useful when the pigmentation stems from chronic inflammation. Prescription-strength retinoids (tretinoin) also reduce pigment, but results typically take five to seven months to become visible. Sunscreen remains the foundation: without daily UV protection, any brightening treatment will be fighting a losing battle.
For vascular dark circles, vitamin C’s collagen-boosting effect can help by thickening the skin enough to better conceal the vessels beneath. Cold compresses temporarily constrict blood vessels and reduce puffiness. Managing allergies or congestion addresses the root cause when venous pooling is the problem.
For structural dark circles caused by volume loss, topical treatments have limited impact because the issue is physical depth, not color. Dermal fillers injected into the tear trough can restore lost volume and eliminate the shadow. This is a cosmetic procedure with results lasting roughly a year, though it carries risks specific to the delicate under-eye area and should be performed by an experienced provider.
Most people have a mix of causes, which is why a combination of sun protection, a targeted topical like vitamin C or azelaic acid, adequate sleep, and hydration tends to produce the most noticeable improvement over time.