When people refer to “bruises under eyes,” they are typically describing chronic dark circles, a common cosmetic concern known medically as periorbital hyperpigmentation or infraorbital discoloration. While a true bruise, or hematoma, results from trauma that breaks blood vessels and causes blood leakage, dark circles are a complex phenomenon with multiple underlying causes. These causes range from inherent anatomical features and genetic predisposition to environmental factors and underlying health conditions. Understanding the specific cause of the discoloration is the first step toward effective management.
Anatomy, Genetics, and Age-Related Changes
The skin beneath the eyes is notably thin, often less than half a millimeter thick. This minimal thickness means that underlying structures are easily visible. When blood flow slows, the deoxygenated blood appears blue or purplish through the translucent skin, creating a phenomenon known as vascular shadowing.
Genetics plays a large role in predisposition to dark circles. Some individuals naturally inherit thinner skin or a higher concentration of melanin in the periorbital area, a condition known as constitutional hyperpigmentation. This inherited tendency is more common in people with darker skin tones prone to producing excess melanin.
The natural aging process further exaggerates this appearance by affecting both skin structure and facial volume. As people age, the skin loses collagen and elastin, thinning the dermis and making blood vessels even more prominent. Age-related changes also include the descent of facial fat pads and bone resorption, which can deepen the “tear trough” deformity. This hollowing effect creates an actual shadow that mimics darkening, making the area appear sunken and discolored regardless of skin pigmentation.
Daily Habits and Environmental Contributors
Daily behaviors and environmental exposure are significant modifiable factors influencing the appearance of periorbital darkness. A lack of restorative sleep is a common culprit, as insufficient rest can make the skin appear paler and duller. This pallor increases the contrast between the skin surface and the underlying blood vessels, making the vascular shadowing more noticeable.
Dehydration also contributes to a sunken, dull appearance because the skin under the eyes is particularly sensitive to fluid imbalance. When the body lacks sufficient water, the skin can lose its plumpness, increasing the visibility of the bony orbital rim and the deep-set eyes. In contrast, a high-sodium diet can cause fluid retention, leading to temporary puffiness or swelling, which casts a shadow that exaggerates the appearance of a dark circle.
Excessive sun exposure stimulates melanocyte activity, causing the body to produce more melanin. This can lead to increased pigmentation in the already susceptible periorbital region, darkening the skin over time. Habitual rubbing or scratching of the eyes causes micro-trauma and inflammation. This trauma can trigger post-inflammatory hyperpigmentation, leaving behind a prolonged patch of darker skin.
Health Conditions Causing Periorbital Darkening
Specific health conditions can directly manifest as noticeable periorbital darkening, often requiring targeted medical management. A frequent cause is the “allergic shiner,” which links nasal congestion to vascular issues under the eyes. When a person experiences allergic rhinitis or sinus congestion, the impaired drainage causes blood to pool in the small veins below the eyes. This stagnant blood flow leads to the dilation of blood vessels, which then appear as a bluish or purplish hue through the thin skin.
Any condition that causes chronic itching, such as eczema or atopic dermatitis, also contributes by prompting frequent eye rubbing. The resulting inflammation and skin damage from rubbing leads to localized post-inflammatory hyperpigmentation.
Anemia, particularly iron deficiency anemia, can also be a factor in periorbital discoloration. Iron is necessary for hemoglobin production, and a deficiency reduces the oxygen-carrying capacity of the blood. The resulting pallor makes the underlying blue-red vasculature more prominent, intensifying the look of dark circles. Other systemic issues, including thyroid conditions or certain medications that cause blood vessel dilation, may similarly contribute to the discoloration.
Options for Reduction and Treatment
Addressing periorbital darkening requires a multi-pronged approach based on identifying the underlying cause. Lifestyle adjustments are the simplest starting point, including ensuring seven to nine hours of restorative sleep each night. Managing chronic allergies with appropriate medication can alleviate congestion and reduce the need to rub the eyes, which minimizes inflammation.
Topical skincare ingredients can target specific aspects of the condition. Products containing Vitamin C act as antioxidants and can inhibit melanin production, helping to lighten pigmented circles. Retinoids, which are Vitamin A derivatives, encourage cellular turnover and collagen production, gradually thickening the thin skin to make blood vessels less visible. Caffeine is a common ingredient that constricts blood vessels, offering a temporary reduction in vascular puffiness and discoloration.
For cases rooted in structural issues, professional interventions may be appropriate. Dermal fillers, typically made of hyaluronic acid, can be injected into the tear trough to restore lost volume and eliminate the shadow cast by the bony orbit. Pigmentation that is resistant to topical treatment may benefit from specific laser treatments designed to break down melanin or target visible blood vessels.