Dark circles under the eyes usually come down to one of a few things: visible blood vessels showing through thin skin, excess pigment deposited in the skin itself, or shadows cast by hollowing beneath the eye. Most adults have some combination of these, and the specific cause shapes what the circles look like, from bluish-purple tones to brown or grayish patches.
Why the Under-Eye Area Is Uniquely Vulnerable
The skin beneath your eyes is some of the thinnest on your body. That means blood vessels sit closer to the surface and are more visible than almost anywhere else. When those vessels dilate or the skin thins further with age, the dark appearance intensifies. This is why dark circles can seem to come and go depending on hydration, sleep, or even the time of day.
Dermatologists generally classify dark circles into three main types based on what’s happening beneath the surface. The first is pigmented, where the skin itself has produced or accumulated more melanin. The second is vascular, where blood vessels or pooled blood create a blue, purple, or reddish tint visible through the skin. The third is structural, where volume loss or shadows from bone and fat changes make the area look darker than it really is. Many people have more than one type at once.
Vascular Dark Circles
If your dark circles look blue, purple, or reddish and seem worse when you’re tired, blood vessels are likely the main culprit. The veins beneath the lower eyelid run close to the surface, and anything that dilates those vessels or makes the overlying skin paler will increase contrast and make them more prominent.
Sleep deprivation is the classic trigger. When you don’t get enough sleep, oxygen levels in the tissues around the eyes drop. Blood vessels dilate in response, and deoxygenated blood appears darker in color. At the same time, poor sleep makes your skin paler overall, which lets those swollen, darker vessels show through more readily. The result: circles that weren’t visible yesterday suddenly appear after a rough night.
Allergies work through a different but related mechanism. When your nasal passages swell from an allergic reaction, they slow blood flow in the veins around the sinuses. These veins sit just beneath the skin under your eyes, and when they become congested and swollen, the area looks darker and puffy. This is common enough to have its own name in medicine: “allergic shiners.” Treating the underlying nasal congestion typically reduces them.
Pigmented Dark Circles
Some dark circles are caused not by visible blood vessels but by the skin itself being darker in that area. This happens when the body deposits extra melanin in the upper or lower eyelid skin, creating a brownish to grayish band that follows the curve of the eye socket. Unlike vascular circles, these don’t change much with sleep or hydration.
Genetics play a major role here. People with darker skin tones are more prone to this type because their skin produces melanin more readily, and the under-eye area seems particularly susceptible. Research on Asian populations found distinct patterns: constitutional (genetic) dark circles were most common in people of Indian and Malay descent, while the vascular type was more prevalent among Chinese individuals. If your parents or siblings have noticeable dark circles, you’re more likely to develop them yourself.
Post-inflammatory hyperpigmentation is another common cause. Any irritation or inflammation around the eyes, whether from eczema, allergic contact dermatitis, or even chronic rubbing, can trigger the skin to overproduce melanin as it heals. This tends to show up as irregular brownish or gray patches, sometimes with visible signs of the underlying skin condition like flaking or thickening. People with darker skin are especially susceptible to this type of pigmentation change.
Structural Changes and Aging
As you get older, the fat pads beneath your eyes gradually shrink. The bone around the eye socket also slowly resorbs over time. Together, these changes create a hollow known as the tear trough, a depression that runs from the inner corner of the eye diagonally down toward the cheek. This hollow casts a shadow that makes the area appear darker even when the skin color itself hasn’t changed.
Skin also loses collagen and elasticity with age, becoming thinner and more translucent. This means blood vessels that were always there become increasingly visible over the years. The combination of hollowing, thinning skin, and gravity pulling tissue downward explains why many people notice dark circles worsening in their 30s and 40s even if they sleep well and have no allergies.
Anemia and Nutritional Deficiencies
Iron deficiency anemia can make dark circles more prominent, though the mechanism is indirect. When your hemoglobin is low, your skin becomes paler. That increased pallor makes the blood vessels beneath the thin under-eye skin stand out in sharper contrast. The circles aren’t caused by a change in the eye area itself but by a change in the canvas around it.
Other nutritional deficiencies, including low levels of vitamin B12 and vitamin K, have been linked to more visible under-eye darkening in some clinical observations, though the evidence is less robust than for iron. If dark circles appear suddenly alongside fatigue, shortness of breath, or unusual paleness, it’s worth checking whether anemia is a factor.
Thyroid Disease and Other Systemic Conditions
In rarer cases, dark circles point to something happening elsewhere in the body. Hyperthyroidism, particularly Graves’ disease, can cause darkening of the eyelid skin. About 2% of people with hyperthyroidism develop hyperpigmentation, which sometimes localizes to the area around the eyes. This is driven by hormonal shifts that increase melanin-stimulating hormone activity. In some people, this periorbital darkening appears before other thyroid symptoms do, making it a potential early sign worth investigating if it develops without an obvious explanation.
Certain medications can also trigger pigment changes around the eyes. If you notice new or worsening dark circles after starting a medication, the drug itself may be contributing.
How to Tell Which Type You Have
A simple test can help you distinguish between the main types at home. Gently stretch the skin beneath your eye and look in a mirror. If the darkening gets worse with stretching, vascular causes are likely dominant, because you’re pressing the skin thinner and making the blood vessels more visible. If the color stays the same or fades slightly, melanin pigmentation is more likely the issue. If the darkness mostly disappears when you tilt your head forward (eliminating the shadow), structural hollowing is the primary cause.
Color also offers clues. Blue or purple tones suggest blood vessels. Brown or grayish tones point toward melanin. A reddish hue, especially with visible tiny blood vessels, indicates superficial capillary involvement. Many people will notice more than one color, which simply means multiple mechanisms are at play.
What Helps Reduce Them
Because the causes differ, what works depends on your type. For vascular circles, consistent sleep (seven to nine hours), managing allergies, staying hydrated, and reducing salt intake to minimize fluid retention can all make a noticeable difference. Cold compresses temporarily constrict blood vessels and reduce puffiness.
For pigmented circles, sun protection is critical. UV exposure stimulates melanin production, and the thin eyelid skin is particularly vulnerable. Wearing sunglasses and applying sunscreen daily to the under-eye area can prevent further darkening. Topical products containing vitamin C or retinoids can gradually lighten existing pigmentation over weeks to months.
Structural dark circles caused by volume loss are the hardest to address with lifestyle changes alone. Injectable fillers placed along the tear trough can restore lost volume and reduce shadowing, with results typically lasting six months to over a year. For more significant hollowing, fat grafting is another option.
When multiple types overlap, combining approaches tends to produce the best results. Someone with both vascular and structural circles, for instance, might benefit from better sleep habits alongside a dermatologist’s assessment for filler. Identifying which mechanism is doing the most work helps you avoid spending time and money on treatments that target the wrong cause.