Dark circles under your eyes form when the thin skin beneath your lower lids reveals the blood vessels, pigment, or shadows underneath. The skin here is less than 1 millimeter thick, making it the thinnest skin on your entire body. That’s why this area shows changes that wouldn’t be visible anywhere else on your face. The cause isn’t always one thing: dark circles fall into a few distinct types, and most people have a combination.
The Three Types of Dark Circles
Not all dark circles look the same, and the color can tell you a lot about what’s going on. Dermatologists generally classify them into three categories based on appearance.
Vascular (blue, purple, or pink): These are caused by blood vessels showing through thin skin. The veins beneath your lower eyelids sit very close to the surface, and when the skin is thin or the vessels are dilated, you see a blue or purple tint. This type is most visible on the inner corner of the eye and tends to look worse during menstruation, when blood flow patterns shift.
Pigmented (brown or black): These result from excess melanin deposited in the skin under the eye. The pigment can sit in the upper or deeper layers of the skin, and it tends to appear as a curved band of brown or black color following the shape of your eye socket. This type is more common in darker skin tones.
Structural (shadow-based): These aren’t caused by color changes at all. They’re shadows cast by the natural contours of your face, particularly when there’s a hollow or depression beneath the eye. If you gently stretch the skin under your eye and the darkness disappears, you’re likely dealing with this type.
Most people have a mix. You might have naturally thin skin that shows blood vessels combined with a slight hollow that casts a shadow, making the area look even darker.
Why Thin Skin Makes It Worse
Your lower eyelid skin is dramatically thinner than the surrounding areas. While the skin on your cheeks and brow is considerably thicker, the eyelid measures less than a millimeter. Underneath that paper-thin layer sits the orbicularis oculi muscle, which you use every time you blink or squint, and a network of tiny blood vessels. There’s very little fat or tissue to act as a buffer between those vessels and the surface.
This is why dark circles can seem to appear overnight after a bad night’s sleep or a long crying session. The vessels haven’t fundamentally changed, but any increase in blood flow or fluid retention makes them more visible through that minimal layer of skin.
How Allergies Cause “Allergic Shiners”
If your dark circles get worse during allergy season or when you’re congested, there’s a specific mechanism at work. When your immune system reacts to allergens, the moist lining inside your nose swells. That swelling slows blood flow through the veins near your sinuses, and those veins run directly beneath the skin under your eyes. When blood pools in those veins, the area looks darker and puffier.
This is why allergists call them “allergic shiners.” The discoloration isn’t from rubbing your eyes (though that can contribute separately). It’s venous congestion, essentially a traffic jam in the tiny veins around your sinuses that makes them visible through your skin. Treating the underlying nasal congestion often reduces the appearance of these circles more effectively than any eye cream.
Rubbing and scratching also play a role over time. Repeated friction from allergies or eczema around the eyes triggers post-inflammatory hyperpigmentation, where the skin responds to irritation by producing extra melanin. This adds a brownish layer on top of the vascular darkening.
Genetics and Skin Tone
Some people are simply born with more prominent dark circles, and genetics are the single biggest factor that determines whether you’ll deal with them. If your parents had visible under-eye circles, you likely will too.
Genetics influence this in several ways. They determine how thin your skin is, how much melanin your body deposits around the eyes, and whether you have a condition called dermal melanocytosis, where pigment-producing cells sit deeper in the skin and create a grey or blue-grey tint. People with darker skin tones are more prone to constitutional pigmentation around the eyes, which shows up as a permanent band of brown or black pigment that follows the curve of the eye socket. This isn’t a sign of anything wrong. It’s just how melanin distributes itself in certain skin types.
What Aging Does to the Under-Eye Area
Dark circles almost always get more noticeable with age, even if you’ve never had them before. Several things happen simultaneously. The skin under your eyes, already the thinnest on your body, loses collagen and becomes even thinner and more translucent. The fat pads that cushion the area begin to shift: some migrate forward, creating puffiness or bags, while the surrounding tissue loses volume and sinks.
This creates what dermatologists call a tear trough deformity, a small depression about 2 to 3 centimeters long that runs from the inner corner of your eye toward the cheek. When this groove deepens, it casts a shadow over the lower eyelid that makes you look tired regardless of how well-rested you are. The bone around your eye socket also loses volume over time, which deepens the groove further. Meanwhile, the ligaments that hold the fat pads in place loosen, allowing the fat to bulge forward and create an uneven surface that makes shadows more pronounced.
This structural type of dark circle doesn’t respond to topical treatments because the problem isn’t color. It’s geometry.
Sleep, Stress, and Other Lifestyle Factors
Poor sleep genuinely does make dark circles worse, though it’s not the root cause for most people. When you’re sleep-deprived, blood vessels dilate and the skin can retain more fluid, both of which make the under-eye area appear darker and puffier. Your skin also looks paler when you’re exhausted, which increases the contrast between your face and those visible blood vessels.
Dehydration works similarly. When your body is low on fluids, the skin under your eyes can look sunken, which deepens shadows. Excessive alcohol and salt intake increase fluid retention, which can make puffiness and vascular dark circles more obvious the next morning. Screen fatigue plays a role too: prolonged eye strain increases blood flow to the muscles around your eyes, contributing to that blue-purple tint.
What Actually Helps
The right approach depends on which type of dark circle you have. A simple test can help you figure it out: gently pull the skin under your eye downward. If the darkness disappears, it’s a shadow problem. If the color stays the same, it’s pigmentation. If it turns a deeper purple or blue, it’s vascular.
For Vascular Dark Circles
Cold compresses constrict the blood vessels and can temporarily reduce the blue-purple tint. Eye creams containing caffeine work on the same principle. In a small clinical trial, pads containing 3% caffeine and vitamin K applied daily for four weeks reduced the appearance of dark circles and improved skin elasticity compared to a placebo. Caffeine narrows blood vessels, while vitamin K supports the clotting process that helps clear pooled blood from under the skin. Getting enough sleep and managing allergies address the underlying causes rather than just the appearance.
For Pigmented Dark Circles
Topical ingredients that reduce melanin production, like vitamin C, niacinamide, and retinoids, can gradually lighten brown pigmentation over weeks to months. Sun protection matters here: UV exposure stimulates melanin production, and the thin under-eye skin is especially vulnerable. A broad-spectrum sunscreen or mineral sunscreen applied daily can prevent pigmented circles from deepening.
For Structural Dark Circles
When the problem is volume loss or hollowing, topical products won’t make a meaningful difference. Dermal fillers injected into the tear trough can restore the lost volume and eliminate the shadow. This is one of the more common cosmetic procedures for under-eye circles, with results lasting roughly a year. For fat pad herniation (bags), the options are more involved and typically surgical.
For all types, a consistent approach matters more than an expensive product. Keeping the under-eye area moisturized helps the skin reflect light more evenly, which can make any type of dark circle less noticeable. And for many people, especially those with genetic or structural causes, some degree of under-eye darkness is simply part of their facial anatomy, not a problem to solve.