Sudden swelling under one eye can feel alarming and uncomfortable. Even a small puffiness can make daily activities awkward and worrying. Whether it’s a noticeable puffiness that doesn’t subside or a tender, red bump that makes blinking difficult, seeing one eye look different from the other naturally raises concern. Understanding what causes swelling under one eye can help you spot warning signs and know when to seek care.
Most cases are mild, but some may require prompt evaluation. Swelling that worsens rapidly, is painful, or comes with fever, discharge, or vision changes should not be ignored. At our emergency room in Pearland, we provide fast assessment and treatment for all types of eye swelling to protect vision and comfort.
Causes of Swelling Under One Eye
Swelling under one eye happens when fluid, infection, inflammation, or tissue changes build up on a single side. Causes are usually localized and can include infections, blockages, trauma, or allergic reactions. Recognizing the signs helps determine whether the issue can be managed at home or requires urgent medical attention.
- Common Symptoms To Watch For
- Puffiness or bulge beneath one eye.
- Redness or warmth around the eyelid.
- Tenderness or mild pain when touched.
- Itching, watery, or crusted eyelids
- Discharge (clear, mucoid, or purulent).
- Vision changes, double vision, or limited eye movement.
- Rapidly worsening swelling or fever.
- Puffiness or bulge beneath one eye.
- Stye (Hordeolum)
A stye is an infection of an eyelash follicle or oil gland, producing a tender bump and swelling under one eyelid. Styes are common and often triggered by rubbing the eyes or poor eyelid hygiene. Weather doesn’t directly cause styes, but increased rubbing during allergy season can contribute. Styes usually resolve within a few days, but untreated styes can grow larger or recur.
- Symptoms
- Tender, localized bump under one eyelid.
- Redness and swelling around the eyelid.
- Pain when blinking or touching the area.
- Possible watery or crusty eyelid.
- Tender, localized bump under one eyelid.
- Chalazion
A chalazion is a blocked meibomian gland that forms a firm, painless lump, often on the lower eyelid, creating visible puffiness beneath one eye. It can follow untreated styes and may persist for weeks. Large chalazia can press on the eye and slightly affect vision if left untreated. Proper eyelid hygiene can reduce the chance of recurrence.
- Symptoms
- Firm, painless lump on the eyelid.
- Mild swelling under one eye.
- Slight pressure or discomfort if large.
- Rarely, blurred vision if pressing on the eye.
- Firm, painless lump on the eyelid.
- Conjunctivitis (Bacterial or Viral Pink Eye)
Conjunctivitis is inflammation or infection of the conjunctiva. It can begin in one eye, causing redness, tearing, discharge, and swelling under that eye. Viral forms are highly contagious, while bacterial infections often remain unilateral initially. Early identification helps prevent the infection from spreading to the other eye or to others.
- Symptoms
- Red, watery eye with swelling under one eye.
- Discharge (clear, mucous, or pus).
- Itching or burning sensation.
- Crusty eyelids, especially after sleep.
- Sensitivity to light.
- Red, watery eye with swelling under one eye.
- Allergic Reaction / Contact Dermatitis
Localized contact with allergens, such as cosmetics, topical creams, or insect bites, can trigger swelling in just one eye. The reaction is often sudden and may include redness, itching, or watery eyes. Identifying the allergen early prevents prolonged swelling and discomfort.
- Symptoms
- Sudden puffiness under one eye.
- Redness or rash around the eyelid.
- Itching or burning sensation.
- Watery or teary eyes.
- Sudden puffiness under one eye.
- Orbital or Preseptal Cellulitis (Emergency)
These infections affect the eyelid or tissues around the eye and can cause rapid swelling in one eye, redness, tenderness, and sometimes fever. Orbital cellulitis is serious and can threaten vision or spread systemically. In fact, vision loss has been reported in about 11% of orbital cellulitis cases
- Symptoms
- Rapid swelling and redness of one eyelid.
- Tenderness or pain when touching the eye.
- Fever or feeling unwell.
- Limited eye movement (orbital cellulitis).
- Eye bulging in severe cases.
- Rapid swelling and redness of one eyelid.
- Insect Bite or Local Trauma
A bite, sting, or blunt injury near one eye can produce localized swelling under that eye, often with redness or bruising. The swelling usually appears within hours and is generally limited to the affected area. Prompt care reduces discomfort and prevents secondary infection.
- Symptoms
- Sudden localized swelling under one eye.
- Redness, bruising, or small puncture marks.
- Mild pain or tenderness.
- Itching if bite-related.
- Sudden localized swelling under one eye.
- Tear Duct Obstruction
Blocked tear ducts in infants can cause mild swelling, tearing, or discharge under one eye, usually unilateral. Persistent blockage can lead to recurrent eye infections if not treated. Left untreated, it may cause chronic irritation, eyelid redness, and occasional secondary infection, so early management is recommended. Early intervention ensures proper tear drainage and prevents discomfort.
- Symptoms:
- Mild swelling under one eye.
- Continuous tearing or watery eyes.
- Sticky or crusty discharge.
- Redness around the inner eyelid.
- Mild swelling under one eye.
- Localized Tumors or Cysts
Benign cysts or tumors in eyelid tissue can cause persistent swelling under one eye. Early identification ensures proper management and prevents complications or growth of malignant lesions. Regular checkups can detect issues before they worsen.
- Symptoms
- Persistent, painless swelling under one eye.
- Firm lump or bump on eyelid tissue.
- Slowly enlarging over weeks or months.
- Occasional mild discomfort or irritation.
- Persistent, painless swelling under one eye.
Under-Eye Swelling in Babies
Babies can develop swelling under one eye from blocked tear ducts, mild allergies, rubbing, or infections. Because they cannot communicate discomfort, caregivers should monitor feeding, behavior, discharge, and warmth around the eye. In rare cases, swelling under one eye may indicate more serious conditions; for example, a study reported 4.8% incidence of eyelid swelling in pediatric SLE cases. Common causes in infants include:
- Blocked tear duct (dacryostenosis).
- Infant conjunctivitis.
- Local skin irritation or contact dermatitis.
- Insect bite or minor trauma.
- Rare congenital cysts or infections.
If you notice persistent swelling or any concerning signs, seek prompt pediatric care to ensure proper evaluation and treatment.
When Is Under-Eye Swelling Dangerous?
Most unilateral under-eye swelling is mild, but certain warning signs indicate serious issues. Swelling accompanied by fever, rapid pain, or vision changes may point to infections or emergencies that threaten vision or health. Immediate evaluation can prevent permanent damage and complications. Prompt treatment is critical for serious cases, and early intervention may save vision. Danger signs:
- Fever, chills, or general malaise.
- Rapidly worsening swelling or pain.
- Vision changes, double vision, or limited eye movement.
- Redness spreads beyond the eyelid.
- Severe headache or facial pain.
- Cuts or punctures near the eye showing infection.
If you notice swelling under one eye or your symptoms worsen, contact Neighbors Emergency Center immediately for expert evaluation and emergency care.
How to Treat Swelling Under One Eye
Treatment depends on the cause and ranges from home remedies to medical interventions.
- Cold Compress: Reduces puffiness and numbs discomfort; helpful for trauma, allergies, or bites.
- Warm Compress: Encourages drainage of blocked glands (styes, chalazia) and soothes inflammation.
- Topical Eyedrops / Artificial Tears: Relieves irritation, flushes allergens, and keeps the eye moist.
- Oral Antihistamines: Reduces allergy-induced swelling and itchiness.
- Topical or Oral Antibiotics: Treat bacterial infections like styes, conjunctivitis, or preseptal cellulitis.
- Prescription Anti-Inflammatories / Steroid Drops: Used briefly for inflammatory eyelid conditions under specialist guidance.
- Incision/Drainage or Minor Surgery: Removes persistent styes, chalazia, abscesses, or cysts.
- Hospital-Level Care (IV Antibiotics, Imaging): Required for orbital cellulitis or severe infections to prevent vision loss and systemic complications.
One Eye Swollen? We Can Help at Neighbors Emergency Center
Swelling under one eye can be uncomfortable and, in some cases, signal a serious underlying condition. Early evaluation is crucial to prevent complications, relieve discomfort, and protect your vision. Identifying the cause promptly ensures the right treatment and peace of mind.
At Neighbors Emergency Center, our skilled team provides rapid assessment and expert emergency care for all types of under-eye swelling. With on-site evaluation and treatment options, we help address the root cause safely, so you can maintain healthy, comfortable eyes and get back to your daily routine with confidence.