A distinct red line, crease, or mark appearing beneath the eye can be visually concerning. The infraorbital area, or skin under the eye, is significantly thinner than the skin elsewhere on the face, making it highly susceptible to showing signs of inflammation, fluid changes, and underlying anatomy. While this symptom is often a temporary cosmetic concern related to lifestyle, it can sometimes be a manifestation of chronic skin conditions or, in rare cases, a sign of a more serious infection. Understanding the difference between these possibilities is the first step toward finding appropriate relief.
Inflammatory and Allergic Triggers
The most common causes for a red line under the eye are rooted in inflammatory responses. One primary culprit is Atopic Dermatitis, commonly known as eczema, which causes the thin under-eye skin to become dry, itchy, and visibly inflamed. This chronic condition leads to skin barrier dysfunction, resulting in patches of redness, scaly texture, and swelling that can follow a crease-like pattern.
Another frequent reaction is Contact Dermatitis, which occurs when the skin encounters an irritant or allergen, triggering an acute inflammatory response. Common triggers include new cosmetic products, fragrances, preservatives in creams, or airborne particles that land on the delicate eyelid area. The resulting reaction can manifest as intense redness, itching, and a defined linear rash where the substance made contact.
Redness in the infraorbital area can also be a symptom of “allergic shiners,” caused by chronic nasal congestion from allergies like hay fever. The swelling inside the nasal passages restricts the drainage of small veins around the sinuses, leading to blood pooling beneath the eyes. This congested, deoxygenated blood shows through the thin skin as a bruise-like or reddish-purple discoloration, emphasizing the natural crease and making it appear as a pronounced line.
Anatomical Features and Lifestyle Factors
In some cases, the appearance of a red or dark line is not due to active inflammation but rather the underlying structure of the face. The skin under the eye is less than a millimeter thick, making the network of tiny blood vessels, or periorbital veins, highly visible. When these vessels are close to the surface, they can create a bluish or reddish tint that follows the bone structure.
The tear trough ligament, a tough band of tissue connecting the skin to the bone along the orbital rim, also plays a role in creating this linear appearance. This ligament forms a natural groove, and when combined with the thin overlying skin, it casts a shadow perceived as a dark or reddish line, especially in certain lighting conditions. Genetics can influence the prominence of this ligament and the thinness of the skin.
Lifestyle factors significantly exacerbate the visibility of these anatomical features and contribute to temporary redness. Lack of sufficient sleep causes blood vessels to dilate and become more prominent, while also increasing the stress hormone cortisol, which can increase inflammation. Temporary fluid retention, often caused by a high-sodium diet or sleeping flat, leads to periorbital edema, or puffiness. This puffiness emphasizes the tear trough groove and makes the area look more red or swollen.
Self-Care Strategies for Reducing Redness
For redness caused by mild irritation, allergies, or lifestyle factors, several self-care strategies can help reduce the appearance of the under-eye line. Applying a cold compress, such as a chilled washcloth or refrigerated tea bags, constricts the superficial blood vessels. This helps reduce vasodilation and localized swelling, temporarily lessening the reddish tint caused by vascular pooling.
Moisture is paramount for maintaining the delicate skin barrier, especially in cases of dryness or mild eczema. Use a hypoallergenic, fragrance-free moisturizer containing ingredients like ceramides, hyaluronic acid, or colloidal oatmeal to soothe the skin and lock in hydration. These ingredients help repair the skin barrier without introducing irritants that can trigger contact dermatitis.
Avoid rubbing or touching the eyes, as this physical friction introduces irritants and causes micro-trauma to the thin skin, worsening inflammation and redness. Managing underlying allergies with over-the-counter antihistamines and using a saline rinse to clear nasal congestion can relieve the pressure that contributes to allergic shiners. Improving sleep hygiene and limiting high-sodium foods, which contribute to fluid retention, will help diminish the morning puffiness that accentuates the under-eye crease.
Identifying Signs Requiring a Doctor Visit
While most instances of under-eye redness are benign, certain accompanying symptoms signal a serious issue that requires prompt medical evaluation. A sudden onset of severe, unilateral swelling (affecting only one eye) may be a sign of a localized infection like periorbital cellulitis. This infection involves the tissues in front of the orbital septum and is characterized by redness and tenderness of the eyelid and surrounding skin.
If the redness is accompanied by severe pain, a fever, bulging of the eyeball (proptosis), double vision, or a decrease in visual acuity, this suggests a deeper condition called orbital cellulitis. Orbital cellulitis is an infection behind the eye’s orbital septum and can lead to serious complications, including vision loss, requiring immediate antibiotic treatment. Any persistent redness, swelling, or discharge that does not improve after one to two weeks of consistent self-care should be evaluated by a healthcare professional.