Dark circles under the eyes are caused by a combination of factors, not just one. The skin beneath your eyes is only about 0.5 mm thick, making it one of the thinnest areas on your body. That thinness means blood vessels, pigment changes, and volume loss all show through more dramatically here than anywhere else on your face. Dermatologists classify dark circles into four types: pigmented, vascular, structural, and mixed, with most people falling into the mixed category.
Genetics and Skin Tone
For many people, dark circles are simply inherited. Genetic factors determine how much melanin your body deposits in the skin beneath your eyes, how thin and translucent that skin is, and how visible the underlying blood vessels appear. If your parents had noticeable under-eye circles, you’re more likely to have them too, regardless of how much sleep you get or water you drink.
People with deeper skin tones tend to have more melanin deposited in the under-eye area, which creates a brownish discoloration. People with lighter skin tones are more likely to see bluish or purplish circles, caused by blood vessels showing through translucent skin rather than by pigment itself. These are two fundamentally different mechanisms that look similar at first glance but respond to different treatments.
Aging and Volume Loss
As you age, three things happen simultaneously in the under-eye area. The skin gets thinner, the fat pads beneath it shrink, and the ligaments holding everything in place stretch and weaken. The result is a hollow, shadowed groove called a tear trough deformity.
The tear trough forms because ligaments that attach the skin to the orbital bone loosen over time. Fat that once provided cushioning beneath the eye atrophies or shifts downward. The bone itself gradually resorbs, deepening the hollow further. Because the skin in this area has very little subcutaneous fat to begin with, even small amounts of volume loss create visible shadows. These shadows cast a dark appearance that has nothing to do with pigment or blood vessels. It’s purely structural, created by light falling into a depression.
This process typically becomes noticeable in your mid-30s to 40s, though it varies widely. Some people develop prominent tear troughs in their late 20s due to naturally thin facial fat pads, while others don’t notice significant hollowing until their 50s.
Allergies and Sinus Congestion
Allergic shiners, the dark, puffy circles that accompany hay fever and other nasal allergies, have a specific vascular cause. When your immune system reacts to allergens, the lining inside your nose swells. That swelling slows blood flow through the veins around your sinus cavities. These veins sit close to the surface of the skin right under your eyes, and when they become congested and dilated, the area looks darker and puffier.
This type of dark circle tends to be bluish-purple and often comes with visible puffiness. It fluctuates with allergy seasons or exposure to specific triggers like dust, pet dander, or pollen. If your dark circles are noticeably worse in spring or after spending time around animals, vascular congestion from allergies is likely a major contributor. Treating the underlying allergy, rather than the circles themselves, is what makes the difference.
Sun Exposure and Eye Rubbing
Ultraviolet light is one of the most significant external triggers for under-eye darkening. UV rays stimulate melanin production, and because the under-eye skin is so thin, even modest sun exposure can cause visible pigment buildup over time. Sun exposure and genetic tendency are considered the two leading causes of excess pigment in this area, which is why consistent sunscreen use is the single most recommended preventive measure for pigment-related dark circles.
Rubbing your eyes contributes through a process called post-inflammatory hyperpigmentation. Any repeated friction or irritation on the skin triggers melanin production as a protective response. If you rub your eyes frequently because of allergies, dryness, or habit, you’re layering pigment damage on top of whatever other factors are already at play. Over months and years, this creates a brownish discoloration that persists even after you stop rubbing.
Iron Deficiency and Anemia
When your body doesn’t have enough iron, your red blood cells carry less oxygen. Poorly oxygenated blood appears darker, and in areas where skin is thin enough to reveal the blood vessels beneath it, that darker blood becomes visible. Iron deficiency anemia can make the under-eye area look noticeably darker or more pale, with tiny blood vessels showing through more prominently than usual.
This type of dark circle often comes alongside other symptoms: fatigue, pale skin elsewhere on the body, shortness of breath during mild activity, and brittle nails. If your dark circles appeared relatively suddenly or worsened alongside these other signs, iron levels are worth checking with a simple blood test.
Salt, Fluid Retention, and Sleep
A high-salt diet causes your body to retain fluid, and that extra fluid often pools in the loose tissue under the eyes overnight. The result is morning puffiness that casts shadows and makes existing circles look worse. Reducing salt intake can visibly decrease this type of fluid-related under-eye swelling. Alcohol has a similar effect, both through dehydration and its tendency to promote fluid retention in facial tissues.
Sleep deprivation contributes in two ways. First, it causes blood vessels to dilate, making them more visible through thin skin. Second, it leads to fluid accumulation around the eyes. But sleep alone rarely explains persistent dark circles. If you’ve optimized your sleep and still have noticeable circles, other factors (genetics, volume loss, pigmentation) are almost certainly driving them.
Why Most People Have Multiple Causes
The mixed type is by far the most common category of under-eye circles. You might have inherited thin skin that reveals blood vessels, accumulated sun-related pigment over the years, and started losing under-eye volume as you’ve aged. Seasonal allergies could be adding vascular congestion on top of all that. Each factor individually might be subtle, but stacked together they create circles that seem resistant to any single fix.
This is why no single eye cream or lifestyle change eliminates dark circles for most people. Topical caffeine can temporarily tighten skin and reduce puffiness, making vascular circles less obvious. Products containing vitamin K target the appearance of visible blood vessels specifically. Sunscreen prevents further pigment buildup. But structural hollowing from volume loss doesn’t respond to any topical product, and genetically determined skin thickness can’t be changed. Understanding which type, or combination of types, you’re dealing with is the first step toward choosing an approach that actually makes a visible difference.