Allergic Conjunctivitis vs Viral Pink Eye,How to Tell Them Apart

Red, watery, uncomfortable eyes are one of the most common presentations in optometry. The umbrella term "pink eye" or conjunctivitis covers several distinct conditions with different causes, different treatments, and different prognoses. The most common forms are allergic conjunctivitis and viral conjunctivitis,and they are frequently confused, leading to inappropriate treatment and prolonged symptoms.

Allergic Conjunctivitis

Caused by an immune response to an airborne allergen: pollen (grass, trees, weeds), dust mites, pet dander, mould spores. In Western Sydney, plane tree pollen is a major seasonal allergen in spring, as is grass pollen in late spring/early summer.

Key features:

• Intense itching,the hallmark symptom. Allergic conjunctivitis itches; viral conjunctivitis usually does not.
• Watery, clear discharge
• Both eyes usually affected simultaneously
• Seasonal pattern or known allergen exposure
• Often associated with hayfever (runny nose, sneezing)
• No fever, no lymph node swelling
• Symptoms improve rapidly with antihistamine eye drops

Viral Conjunctivitis

Usually caused by adenovirus, and often follows or accompanies an upper respiratory tract infection (cold). It is highly contagious and spreads through contact with eye secretions.

Key features:

• Watery discharge,typically copious and clear, not purulent
• Gritty rather than itchy
• Usually starts in one eye and spreads to the other within 1–3 days
• Swollen lymph nodes in front of the ear (preauricular lymphadenopathy)
• Recent cold or URI
• Very contagious,strict hygiene measures required
• Antibiotic drops have no effect on viral conjunctivitis

Bacterial Conjunctivitis

Produces thick, yellow-green purulent discharge (not watery), causing eyelids to stick together,particularly in the morning. More common in children. Responds well to antibiotic drops that Dr Tahiri can prescribe directly.

Treatment

• Allergic: Antihistamine or mast cell stabiliser eye drops (prescribed or selected by Dr Tahiri), oral antihistamines, avoidance of the triggering allergen
• Viral: Supportive care (cold compresses, lubricant drops), strict hygiene to prevent spread, no antibiotic drops needed
• Bacterial: Antibiotic eye drops prescribed by Dr Tahiri