What causes swelling eyes, possibly due to allergies or other factors?

Causes of Eye Swelling

Eye swelling has multiple causes, with allergic conjunctivitis being the most common benign etiology, but you must immediately rule out sight-threatening and life-threatening conditions like orbital cellulitis, preseptal cellulitis, and malignancy before attributing symptoms to simple allergies.

Immediate Red Flag Assessment

Before considering allergies, you must evaluate for emergent conditions that require immediate intervention:

• Orbital cellulitis presents with proptosis, painful eye movements, vision loss, or fever and requires immediate hospitalization, contrast-enhanced CT of orbits and sinuses, IV antibiotics, and urgent consultation with ophthalmology, otolaryngology, and infectious disease 1
• Preseptal cellulitis causes upper eyelid swelling without orbital signs and requires high-dose amoxicillin-clavulanate with daily follow-up until definite improvement, with hospitalization for IV antibiotics if no improvement in 24-48 hours or progressive infection 1
• Ethmoid sinusitis with periorbital extension should be considered especially with medial canthal swelling, purulent nasal discharge, and facial tenderness, with key examination finding of purulent exudates in the middle meatus 1

Allergic Causes

If red flags are absent, allergic etiologies are the most common cause of eye swelling:

• Seasonal and perennial allergic conjunctivitis affects 40-80% of people with allergic symptoms, causing itchy, watery eyes, runny nose, sneezing, and itching of the nose or throat 2, 3
• Seasonal allergic conjunctivitis responds to simple treatment with antihistamines (such as diphenhydramine), anti-inflammatory agents, or cromoglycate 3
• Perennial allergic conjunctivitis requires longer therapy with mast cell stabilizers and sometimes local steroids 3
• Giant papillary conjunctivitis occurs in contact lens users or patients with sutures following ocular surgery, presenting as a foreign body reaction, and treatment includes discontinuing contact lens wear, switching to daily disposables, and using preservative-free solutions 1, 3
• Contact allergic blepharoconjunctivitis is often caused by cosmetics and eye medication 3

Non-Allergic Inflammatory Causes

Several non-allergic conditions can mimic allergic eye swelling:

• Floppy eyelid syndrome presents with upper eyelid edema, easily everted upper lid, and horizontal lid laxity, associated with obesity, sleep apnea, and thyroid disease 1, 4
• Atopic keratoconjunctivitis requires long-term treatment of lid eczema and keratoconjunctivitis 3
• Vernal keratoconjunctivitis mainly affects children and young people, commonly calms down after puberty, and demands intensive therapy to avoid serious complicating corneal ulcers 3
• Nonallergic eosinophilic conjunctivitis affects mostly middle-aged and older women with eosinophilic conjunctivitis and dry eye 3

Corneal Causes of Eye Swelling

Corneal edema can present with periocular swelling and specific symptoms:

• Corneal edema presents with blurred or variable vision with diurnal character (worse upon waking and clearer later in the day), photophobia, redness, tearing, and intermittent foreign-body sensation 5
• Elevated intraocular pressure (often from topical corticosteroid treatment), moderate to severe corneal or intraocular inflammation, and corneal hydrops associated with keratoconus can cause acute corneal edema 5
• Inflammatory and pressure-related corneal edema often clears as the underlying problem resolves 5

Malignancy Warning Signs

Chronic unilateral presentation unresponsive to standard therapy demands immediate biopsy, as sebaceous carcinoma can masquerade as chronic unilateral blepharoconjunctivitis 1, 6:

• Biopsy indications include unifocal recurrent lesions, resistance to therapy, focal lash loss, and chronic unilateral presentation unresponsive to treatment 1
• Gradual enlargement over weeks to months, central ulceration or induration, irregular borders, eyelid margin destruction or loss of lashes, and telangiectasia are red flags for malignancy 6

Common Pitfalls to Avoid

• Do not attribute all eye swelling to allergies without first ruling out infectious causes, particularly in patients with fever, progressive swelling, or systemic symptoms 1
• Work-related ocular allergies should be considered as a cause of resistant ocular symptoms in workplaces 3
• Many systemic medications can contribute to ocular surface dysfunction and swelling, including amantadine for neurologic disease and topical chlorhexidine preparation 5